HP MSA Remote Snap Software - Technical white...

MSA Remote Snap Software

Technical white paper

Technical white paper

Contents

Introduction.......................................................................................................................................................................................................................................................................................................................................5
Remote Snap product overview...............................................................................................................................................................................................................................................................................5

What’s new?.....................................................................................................................................................................................................................................................................................................................................6
Benefits of Remote Snap......................................................................................................................................................................................................................................................................................................6

Disaster recovery ..................................................................................................................................................................................................................................................................................................................6
Backup............................................................................................................................................................................................................................................................................................................................................6
Development ............................................................................................................................................................................................................................................................................................................................ 6
Components of Remote Snap...........................................................................................................................................................................................................................................................................................7
Components common to linear and virtual replication.......................................................................................................................................................................................................................7
Components of linear replication............................................................................................................................................................................................................................................................................7
Components of virtual replication ..........................................................................................................................................................................................................................................................................7
How the technology works.................................................................................................................................................................................................................................................................................................8
Comparison of linear replications versus virtual replications............................................................................................................................................................................................................12
Types of replications..............................................................................................................................................................................................................................................................................................................12
Local replication...................................................................................................................................................................................................................................................................................................................12
Remote replication ............................................................................................................................................................................................................................................................................................................12
Physical Media Transfer...............................................................................................................................................................................................................................................................................................12
Remote Snap requirements.............................................................................................................................................................................................................................................................................................13
Setup requirements..........................................................................................................................................................................................................................................................................................................13

Linear replications.......................................................................................................................................................................................................................................................................................................13
Virtual replications......................................................................................................................................................................................................................................................................................................13
Restrictions common to both linear and virtual replications................................................................................................................................................................................................13
Network requirements...................................................................................................................................................................................................................................................................................................14
Remote Snap basic functions.........................................................................................................................................................................................................................................................................................15
General notes about using the SMU.................................................................................................................................................................................................................................................................15
Performing tasks using the v2 SMU............................................................................................................................................................................................................................................................18
Performing tasks using the v3 SMU............................................................................................................................................................................................................................................................18
Preparing the systems...................................................................................................................................................................................................................................................................................................18
Adding a remote system for linear replication ..................................................................................................................................................................................................................................18
Creating a peer connection for virtual replication..........................................................................................................................................................................................................................19
Creating a replication set............................................................................................................................................................................................................................................................................................20
Creating a linear replication set .....................................................................................................................................................................................................................................................................20
Creating a virtual replication set.....................................................................................................................................................................................................................................................................22

Technical white paper

Scheduling replications .................................................................................................................................................................................................................................................................................................25
Common schedule parameters........................................................................................................................................................................................................................................................................25
Scheduling a linear replication.........................................................................................................................................................................................................................................................................25
Scheduling a virtual replication ......................................................................................................................................................................................................................................................................28

Deleting a replication set............................................................................................................................................................................................................................................................................................30
Deleting a linear replication set using the SMU..............................................................................................................................................................................................................................30
Deleting a virtual replication set using the SMU.............................................................................................................................................................................................................................31
Deleting a replication set using the CLI...................................................................................................................................................................................................................................................31

Accessing the secondary volume’s data........................................................................................................................................................................................................................................................32
Exporting a replication image of a linear replication volume...............................................................................................................................................................................................32
Creating a snapshot of a virtual replication volume.....................................................................................................................................................................................................................33

Setting the primary volume (linear replications only)......................................................................................................................................................................................................................34
Verifying replication data links...............................................................................................................................................................................................................................................................................35
Ports connected for replication ...........................................................................................................................................................................................................................................................................40

Connected port field in a linear replication set ...............................................................................................................................................................................................................................40
Connected ports listed for a peer connection for virtual replications.........................................................................................................................................................................42
CHAP settings and Remote Snap.......................................................................................................................................................................................................................................................................43
Examples of replication types and operations ..............................................................................................................................................................................................................................................45
Remote replication ...........................................................................................................................................................................................................................................................................................................45
Local replication and Physical Media Transfer (for linear replications only)..............................................................................................................................................................46
Disaster recovery operations..................................................................................................................................................................................................................................................................................47
Linear replications......................................................................................................................................................................................................................................................................................................47
Virtual replications.....................................................................................................................................................................................................................................................................................................50
Use cases.........................................................................................................................................................................................................................................................................................................................................54
Single office with a remote site for backup and disaster recovery using iSCSI to replicate data .............................................................................................................54
Single office with local site disaster recovery and backup using iSCSI and host access using FC..........................................................................................................56
Single office with a local site disaster recovery and backup using FC (linear replications only) ...............................................................................................................57
Two branch offices with disaster recovery and backup.................................................................................................................................................................................................................58
Single office with a target model using FC and iSCSI ports........................................................................................................................................................................................................59
Multiple local offices with a centralized backup (linear replications only) ....................................................................................................................................................................60
Replication of application-consistent snapshots (linear replications only) ...................................................................................................................................................................61
Replication of the Microsoft VSS-based application-consistent snapshots (linear replications only).................................................................................................64
Best practices...............................................................................................................................................................................................................................................................................................................................66
Fault tolerance......................................................................................................................................................................................................................................................................................................................66
Volume size and policy.................................................................................................................................................................................................................................................................................................66

Technical white paper

For linear replications..............................................................................................................................................................................................................................................................................................66
For virtual replications............................................................................................................................................................................................................................................................................................67
License ........................................................................................................................................................................................................................................................................................................................................ 67
Scheduling ...............................................................................................................................................................................................................................................................................................................................67
Linear replications......................................................................................................................................................................................................................................................................................................67
Virtual replications.....................................................................................................................................................................................................................................................................................................68
Physical media transfer (linear replications only)................................................................................................................................................................................................................................68
Replication setup wizard (linear replications only).............................................................................................................................................................................................................................69
Application-consistent snapshots (linear replications only)......................................................................................................................................................................................................69
Max volume limits .............................................................................................................................................................................................................................................................................................................69
Replication limits ................................................................................................................................................................................................................................................................................................................70
Monitoring.................................................................................................................................................................................................................................................................................................................................71
Replication..........................................................................................................................................................................................................................................................................................................................71
Events.....................................................................................................................................................................................................................................................................................................................................71
Performance tips.................................................................................................................................................................................................................................................................................................................72
Troubleshooting.........................................................................................................................................................................................................................................................................................................................72
FAQs .....................................................................................................................................................................................................................................................................................................................................................73
Summary...........................................................................................................................................................................................................................................................................................................................................75
Glossary..............................................................................................................................................................................................................................................................................................................................................75
For more information............................................................................................................................................................................................................................................................................................................76

Technical white paper Page 5

Introduction

This document provides information for using the MSA Remote Snap Software (Remote Snap). The following topics are covered:

• Benefits
• Components
• How the technology works
• Types of replications
• Requirements
• Basic functions
• Use cases
• Best practices
• Troubleshooting
• Frequently asked questions

Remote Snap product overview

Remote Snap is array-based functionality that provides remote replication on HPE MSA 2040 Storage, HPE MSA 1040 Storage, and HP P2000
G3 arrays. The following array controllers support Remote Snap:

• MSA 2040 SAN Controller
• MSA 1040 FC Controller
• MSA 1040 1 Gb iSCSI Controller
• MSA 1040 10 Gb iSCSI Controller
• P2000 G3 MSA Fibre Channel Controller
• P2000 G3 MSA FC/iSCSI Combo Modular Smart Array Controller
• P2000 G3 10 GbE iSCSI MSA Array System Controller
• P2000 G3 iSCSI MSA Array System Controller
Please visit hpe.com/storage/MSA2040, hpe.com/storage/MSA1040 or hpe.com/storage/P2000 for more information on these controllers.

Note

Remote Snap is not supported on the P2000 G3 SAS MSA Array System Controller, the MSA 1040 SAS Controller or the MSA 2040 SAS
Controller.

Remote Snap is a form of asynchronous replication that replicates block-level or page-level data from a volume on a primary system to a
volume on a secondary system. The secondary system may be at the same location as the first, or it may be located at a remote site. Remote
Snap uses the snapshot functionality of the array to replicate the block-level or page-level data, only replicating blocks or pages that have
changed since the last replication, thereby providing efficient replication.

Technical white paper Page 6

What’s new?

This section describes new enhancements and support added with the release of the GL220 firmware for MSA 1040 and MSA 2040 Storage.

• Replicate virtual volumes, snapshots, or volume groups between MSA 2040 Storage and MSA 1040 Storage using iSCSI. Virtual volume
replication replicates page-level data, while linear replication replicates block-level data.

With the addition of Remote Snap for virtual volume replication, information specific to Remote Snap for linear volume replications will use the
abbreviated term linear replication, while information specific to virtual volume replications will use the abbreviated term virtual replication.
Linear replications cannot coexist with virtual replications on a system.

Benefits of Remote Snap

Remote Snap is a licensed replication feature for disaster recovery. It has a robust, fault-tolerant design that allows replication to continue in the
event of some system failures involving communication, controllers, ports, hard drives (depending on the RAID configuration), or temporary power
failure. Remote Snap can employ Ethernet or, for linear replications only, Fibre Channel (FC) technology.

Remote Snap technology enables the following key data management and protection capabilities:

• Continuity of business systems in the event of a failure on the primary site

• Access to data at a remote site, for either dispersed operations or development activities

• Multiple recovery points using snapshots

Disaster recovery

Remote Snap provides access to data at a secondary site when the primary site experiences a critical failure. It allows several data volumes
(limits determined by model and volume type replicated) to be replicated. Replicating at regular intervals helps to protect the data. Recovery
time is reduced because the data is available at the secondary site; applications can switch to the secondary site with minimal downtime using
data from the last replication point. The data stored at the secondary site can then be used to restore the primary location once it is back
online, or the data can be exported and used by users at the secondary site.

Backup

Remote Snap can replicate volumes with marginal impact on server performance. It can be used by small businesses as a primary backup tool
and by large businesses as a secondary backup tool at data centers. Remote Snap can be used as interim storage for backing up to removable
media such as tape.

Alternatively, remote offices can replicate to central data centers where backups occur. The software reduces the overall backup time by
replicating only data that has been modified. Because linear volume replication supports either FC or Ethernet interconnects, businesses have
the flexibility to use the technology that best matches their current environment.

Development

Remote Snap enables different development use cases:

• An application administrator can test patches or changes in the primary system by switching the applications to the secondary site. Once
the testing of the patch update is completed, the administrator can switch the applications back to the primary site.

• A database application development team can have access to regularly scheduled snapshots of the replicated database volumes by exporting
the snapshots on the secondary system. When the exported snapshot is no longer needed, it can be deleted.

Technical white paper Page 7

Components of Remote Snap

Components common to linear and virtual replication

• Primary volume—the volume that is the source of the replication. This volume can be mapped to hosts. For virtual replications, the primary
can be a virtual volume, a virtual snapshot, or a virtual volume group.

• Secondary volume—the volume that is the destination or target of the replication. This volume cannot be mapped to hosts, but it can be
snapped, and the snapshot can be mapped to hosts. For virtual volumes, this can be either a virtual volume or virtual volume group.

• Primary and secondary volume replication snapshots—snapshots of the primary or secondary volume used in replication. Replication
snapshots do not count against license limits.

For linear replications, these snapshots are listed in the output of the user interfaces; though they cannot be directly mapped to hosts, they can
be exported as regular snapshots, and those snapshots can be mapped to hosts. As you’ll see below, linear replications can have a number of
replication snapshots—if a replication snapshot of a primary volume has a matching secondary volume replication snapshot, the two replication
snapshots are together considered a replication image.

For virtual replication, there are two snapshots, the current snapshot and the previous snapshot. Though these snapshots are not listed, they
do consume space and count against volume count limits for snapshot trees and pools.

• Replication set—a primary and secondary volume pair connected together for the purposes of replication, along with their associated snapshots.

For linear replications, the replication set includes the host I/O ports used for replication for the set. Each replication set may have different host
I/O ports used. The direction of a linear replication set can be changed—the secondary becomes the primary and the primary becomes the
secondary.

For virtual replication, the replication set includes the peer connection used. See below for more information on the peer connection. The
direction of a virtual replication cannot be changed—the secondary cannot become the primary and the primary cannot become the secondary.
Also, if the replication set includes a virtual volume group, you cannot add or remove volumes from the volume group.

Components of linear replication

• Remote system—a representation of another array; it contains the management IP addresses and login credentials of a management level
user on that array. The local array may communicate using the management ports to the remote array to obtain storage configuration of the
remote array to assist in creating and managing replication sets.

• Replication image—a conceptual term for a pair of primary and secondary snapshots that represent a synchronized point-in-time representation of
the data.

Components of virtual replication

• Peer connection—defines the ports used between two arrays involved in replications. These ports are used for managing replications as well
as transferring data for replication; the management ports of the array are not used for virtual replication. Peer connections are bi-directional,
and can use iSCSI ports only. All replications that share a peer connection use the same ports. An array may have only one peer connection.

Technical white paper Page 8

How the technology works

Remote Snap is based on the existing snapshot technology offered by MSA 2040 Storage, MSA 1040 Storage, and P2000 G3 arrays.
Snapshots are used to track the data to be replicated by determining the differences in data updated on the master volume, minimizing the
amount of data to be transferred.

Remote Snap enables snapshots of data to reside on another array at a location other than the primary site. To perform a replication, the
system takes a snapshot of the volume to be replicated, creating a point-in-time image of the data. The system replicates this point-in-time
image to the destination volume by copying only the differences in the data between the current snapshot and the previous one via TCP/IP
(iSCSI) or FC.

The snapshot occurs at the volume level and is block-based or page-based. The software functions independently of the vdisk or disk group
RAID and drive configuration, so the secondary volume in a given set may have different underlying RAID levels, drive counts, drive sizes or
drive types than the primary volume, though the volume sizes are identical. Since the software functions at the raw block-level or page-level,
it has no knowledge of the volume’s operating system configuration, the file system, or any data that exists on the volume.

Linear replication uses a pull model while virtual replication uses a push model. In a pull model, the secondary volume’s system requests data
from the appropriate snapshot on the primary volume; in a push model the primary volume’s system writes data to the appropriate snapshot
on the secondary volume.

The linear replication process includes the following steps:

1. Create a snapshot on the primary volume. This snapshot is a component of a replication image.

2. The primary array sends a notification to the designated secondary array that a replication operation has been started for a given storage
volume.

3. The secondary array requests a difference list from the primary array. This list contains only the changed storage blocks of the primary
volume since the last replication command (previous sync point snapshot). For the first replication, the difference list contains all storage
blocks of the primary volume.

4. The primary array sends a difference list to the secondary array.

5. The secondary array requests all blocks in the difference list from the primary array.

6. When the transfer is complete, the secondary array creates a new snapshot to track the newly acquired storage blocks. The secondary
array creates snapshots of the secondary volume for each replication.

Linear replication repeats step 1 and queues steps 2-6 for each new replication command issued to the same replication set until the prior
replication command is complete. As long as the sync points are maintained, new replication commands to the same primary volume can be
performed while one or more previously executed replication commands are still in process. This enables you to take snapshots at discrete
intervals without waiting for any previous replications to complete.

Technical white paper Page 9

Replication Image Creation Cycle

Application Server

I/O Path Management I/O Path
Local Array Network Remote Array

Replication Connection Topology

I/O I/O

Primary Volume One Complete Replication Set Second Volume

12 replication activity 3 Snapshot
Initial replication synch point set
Sna psh ot 4 Common replication synch point set actions
actions Latest replication synch point set
56
First replication image
First replication image
12
62
Second replication image
Second replication image
1n
6n
Latest replication image
Latest replication image

Customer can perform more replication New replication request Subsequent replication on same
prior to completion of previous. Local Array creates local replication source volume will be queued and
snapshot of primary volume. pause until previous complete.
Replication command completes by
saving all transferred blocks into a 1 Local Array informs Remote
replication image and takes a Array of new replication request.
snapshot of the secondary volume. 6 Replication 2
Now a replication synch point set Image creation Remote Array requests a
exists on source and remote arrays. process change list since last replication.

54 3

Remote Array requests changed list; first replication contains all
blocks from Local Array. Before blocks in the volume.
first replication completes, the
secondary volume is reported as
‘replication prepare volume’.

Figure 1. Linear replication image creation cycle

Technical white paper Page 10

The process for virtual replication includes the following steps:

1. Save the previous snapshots of the primary and secondary volumes.
2. Create current snapshots of the primary and secondary volumes,
3. Compare the current primary snapshot to the previous primary snapshot.
4. Copy the differences to the current secondary snapshot. For the initial replication, all allocated pages are copied, but only allocated pages—

no copying of empty unallocated pages. For subsequent replications, only the difference between the current primary snapshot and
previous primary snapshot are copied.
5. Rollback the secondary volume to the current secondary volume snapshot.

Virtual replication does not queue replications; if a new replication request occurs while a previous replication is in process, the new request fails.
Virtual replication does not keep more than the current and previous snapshots, and those snapshots are not accessible.

Technical white paper Page 11

Figure 2. Virtual replication cycle

Technical white paper Page 12

Comparison of linear replications versus virtual replications

FEATURE/ATTRIBUTE LINEAR REPLICATION VIRTUAL REPLICATION
iSCSI or FC iSCSI
Replication protocol All blocks are copied Only allocated pages are copied
Initial replication Up to the maximum number of snapshots Not applicable—only the current replication is
Allowed retained
Multiple replication images Allowed Not allowed

Modify primary volume/reverse replication direction Not allowed Not allowed
Replicate snapshot of the primary volume using Allowed
existing replication set Allowed
Create replication set using a snapshot or a volume
group as the source Not allowed
Can replicate to or from more than one system

Types of replications

A replication from a volume on a system to another volume on the same system is a local replication; a replication from a volume on one system to
a volume on another, separate, system is a remote replication, no matter the location of the primary or secondary system. Virtual replication can
perform remote replications, while linear replication can perform both local and remote replications, and can be reconfigured between the two.

Local replication

Local replication occurs when the primary and secondary volumes reside on the same system. When creating the replication set, ensure the
primary volume resides on one vdisk and the secondary volume resides on another vdisk. Once the set is created, replications can be initiated.

Remote replication

Remote replication occurs when the primary and secondary volumes reside on different systems. When creating the replication set, ensure the
primary volume resides on a vdisk or pool of the local, or primary, system and the secondary volume resides on a vdisk or pool on the remote,
or secondary, system. Once the set is created, replications can be initiated.

Physical Media Transfer

Another option for linear replication is to perform an initial local replication before converting to a remote replication as part of a disaster
recovery setup or backup. The initial replication between a primary linear volume and a secondary linear volume requires a full data copy
between the two volumes; every block on the volume is copied. If the primary volume is very large, even if there is very little actual data written
to it, the initial remote replication can take a long time to complete and can cause bandwidth congestion. Perform a local replication to avoid
congestion, and then transfer the secondary volume to the remote system by transferring the physical media that the secondary volume
resides on to the remote system. This process is known as Physical Media Transfer.

Note that when using Full Disk Encryption (FDE) on an MSA 2040 Storage array, it is a best practice to move media between systems that are
identically configured with FDE enabled or disabled. That is, move secured Self-Encrypting Drives (SED) to a secured FDE system, and unsecured
SEDs or non-SEDs to an unsecured FDE system or non-FDE system.

Technical white paper Page 13

Remote Snap requirements

Setup requirements

To set up Remote Snap, observe the following requirements:

Linear replications
• One, for local replications, or two, for remote replications, dual-controller arrays connected via a switch; direct connection between systems is

not supported. For optimum results, configure and connect all ports.

• The management ports on the two arrays must be on the same network when using the SMU to create replication sets, or when specifying a
vdisk and having the remote system create the secondary volume.

• The Remote Snap license must be enabled on the local and, if applicable, remote systems:

– To explore Remote Snap, enable the 60-day temporary license available on the P2000 G3 SMU on the system’s Tools > Install License
page, or obtain a 180-day temporary license.

– To permanently enable Remote Snap, purchase a license.

• Remote Snap supports up to 16 replication sets per array (up to 8 replication sets for the MSA 1040 Storage array). If a volume on the
system is participating in a replication set, either as a primary volume or as a secondary volume, it counts against the replication set limit.

• For the combo controller and iSCSI controller arrays, for optimal results connect and configure all of the iSCSI ports with valid IP addresses.

• At least one volume on the primary system and one vdisk on the secondary system are required to create a replication set.

• For linear replication, creating replication sets with the SMU requires adding the remote system to the local, or primary, system. Creating
replication sets with the CLI is easier if the remote system is added, but is not necessary.

• If using an existing replication-prepared volume, it must be the exact same size as the primary volume.

Virtual replications
• Two arrays are required. All arrays should have all ports configured and connected via a switch; direct connection between systems is not supported.

• The Remote Snap license must be enabled on both systems:

– To explore Remote Snap, obtain a 180-day temporary license.

– To permanently enable Remote Snap, purchase a license.

• Remote Snap supports up to 32 replication sets per array. If a volume on the system is participating in a replication set, either as a primary
volume or as a secondary volume, it counts against the replication set limit

• At least one virtual pool on each system is required to create a peer connection between the two systems.

• At least one volume on the primary system is required to create a replication set.

Restrictions common to both linear and virtual replications
Remote Snap does not support SAS. Refer to the Remote Snap product overview section in the Introduction (page 5).

Note

For more information on controller types and additional specifications, see the HPE MSA 2040 Storage QuickSpecs, the HPE MSA 1040 Storage
QuickSpecs, or the HPE MSA P2000 G3 Modular Smart Array Systems QuickSpecs

Technical white paper Page 14

Network requirements

The following is a guideline for setting up iSCSI controllers with 1 Gb and 10 Gb ports to use with Remote Snap. The two arrays do not have to be in
the same subnet, but must be connected to a network whose route tables and firewall or port-blocking settings allow iSCSI traffic (port 3260) to
pass between the two systems.

System or environment variables

Hardware type: 10 Gb or 1 Gb
Priority (set from set replication-volume-parameters priority): Low, Medium, or High
Number of concurrent inbound replications (Rp) (from the primary system’s view): User-configured
Number of inbound channels (Cp) (from the primary system’s view): User-configured
Number of concurrent outbound replications (Rs) (from the secondary system’s view): User-configured
Number of outbound channels (Cs) (from the secondary system’s view): User-configured
Packet loss rate (PL): You may get this from a switch or router, or use a tool such as PathPing or MTR.
Round trip time (RTT) in ms: Get this from ping
Bandwidth (BW) in Kilobytes/second (Kbps): Use a bandwidth speed test available from many websites.
Congestion Avoidance Loss (CAL): This is difficult to obtain. It is generally around 30 percent for a WAN, but higher as distance increases.
Throughput requirements
Data Transfer Pending (DTP) depends on the Priority: 1280 for low, 2816 for medium, or 4096 for high.

Primary system calculations:

Primary timeout (TOp): 30 ms
Throughput required (Tp) = DTP * Rp/TOp
Minimum throughput required (MTp) = 13 KB/s
Secondary system calculations:

Secondary timeout (TOs): 40 ms
1 Gb throughput required (Ts): DTP * Rs (up to 8)/TOs
10 Gb throughput required: N/A
Minimum throughput required (MTs) = 9.6 KB/s
Network throughput

Maximum segment size (MSS): 8960 if Jumbo frames are enabled, 1460 otherwise
TCP window size (TWS) in Kilobytes: 32 KB for 1 Gb controllers, 64 KB for 10 Gb controllers
Throughput limit by packet loss (Bps): If PL = 0, then 0, else MSS/ (RTT/1000) * (1/SQRT [PL])
Throughput limit by RTT (Bps): TWS/(RTT/1000) * (1-CAL)
Throughput limit by Bandwidth (Bps): BW * 1024
Network throughput limit (NTL): Minimum of throughput limit by packet loss (if non-zero), throughput limit by RTT and throughput limit by
bandwidth

Technical white paper Page 15

Results

Primary system throughput required to avoid timeout (TOAp) (KB/s) = Tp/Cp

For the primary system

• If the NTL is greater than the TOAp, the replication should not timeout.
• If the NTL is greater than the MTp, timeouts will occur, but the replication should succeed.
• If the NTL is less than the MTp, the replication will fail.

Secondary system throughput required to avoid timeout (TOAs) (KB/s) = Ts/Cs for 1 Gb controllers, N/A for 10 Gb controllers.

For the secondary system with 1 Gb controllers

• If the NTL is greater than the TOAs, the replication should not timeout.
• If the NTL is greater than the MTs, timeouts will occur, but the replication should succeed.
• If the NTL is less than the MTs, the replication will fail. If the secondary system contains 10 Gb controllers, then the replication should not

timeout.

Remote Snap basic functions

The following functions are highlighted in this section:

• Preparing the systems:
– For linear replication, adding a remote system
– For virtual replication, creating a peer connection

• Creating a replication set
• Scheduling replications
• Deleting a replication set
• Accessing the secondary volume’s data

– Exporting a replication image of a linear replication set
– Creating a snapshot of a secondary virtual volume
• For linear replication, setting the primary volume
• Verifying replication data links

For more information on Remote Snap functions, see the HPE MSA 2040 SMU reference guide, the HPE MSA 1040 SMU reference guide, or the
HP P2000 G3 MSA System SMU reference guide.

General notes about using the SMU

Linear replications are created and managed using the v2 version of the SMU and CLI; virtual replications are created and managed using the v3
version of the SMU and CLI. The P2000 G3 supports only the v2 version of the SMU and CLI; the MSA 1040 and MSA 2040 support both versions.
For the CLI, see the current version (v2 or v3) using the show cli-parameters command and set it using the management-mode parameter
of the set cli-parameters command. For the SMU, specify v2 or v3 in the URL (e.g. https://10.10.0.10/v2), or change the version on the login
screen as necessary—click the link “Click to launch previous version.” on the v3 login screen to access the v2 interface, or click the “Click to launch
new version of the application.” on the v2 login screen to access the v3 interface.

Technical white paper Page 16

Figure 3. Selecting the v2 interface from the v3 login

Technical white paper Page 17

Figure 4. Selecting the v3 interface from the v2 login

Technical white paper Page 18

Performing tasks using the v2 SMU
To perform a task, select the component in the Configuration View panel and then either right-click on the component and use the context
menu, or click a task category from the list at the top of the main panel and select the specific task to perform. The system is the top-most
component of the Configuration View panel and shows the system’s name and its model in parentheses.

Performing tasks using the v3 SMU
To perform a task, select the topic from the topic tabs on the left side of the interface, select the component in the topic pane, then select the
action from the Action menu. While some tasks may be performed in the Volumes topic, all tasks can be performed in the Replications topic.

Preparing the systems

Adding a remote system for linear replication
This operation adds the remote system to the local system. The remote system is listed in the navigation tree. This operation is required when
using the SMU to create a replication set. This operation is required when using the CLI only when specifying a remote vdisk and having the
remote system create the secondary volume; however, adding a remote system generally makes it easier to create a replication set using the
CLI. Use the system’s Configuration > Remote Systems > Add Remote System SMU page or the create remote-system CLI command.

Figure 5. Creating a remote system using the SMU

Technical white paper Page 19

# create remote-system username manage password !manage 10.10.5.170
Success: Command completed successfully. (10.10.5.170) - The remote system was created.

Command example 1 Creating a remote system using the CLI

Creating a peer connection for virtual replication
This operation creates a connection between two systems for the purpose of replication. The connection uses the iSCSI host ports for both
communication and I/O. The connection includes all paths between the systems—it uses up to two paths for load balancing. The connection is
bi-directional—the concepts of primary and secondary do not apply to the connection. Only one peer connection can exist on a system—thus,
there is a one-to-one relationship between systems, unlike linear replication which can have up to four systems participating in replications
between them. In the Replications topic, select Action > Create Peer Connection. The Create Peer Connection panel opens. Enter a name for the
connection and the iSCSI address of one of the ports of the other system. Alternatively, use the create peer-connection CLI command.

Figure 6. Creating a peer connection using the SMU

Technical white paper Page 20

# create peer-connection remote-port-address 10.20.5.162 PhxSea
Info: This may take a few minutes to ping all port combinations...
Success: Command completed successfully.

Command example 2 Creating a peer connection using the CLI

Creating a replication set

Creates the secondary volume if necessary and connects it to the primary volume. When creating a replication set, you must always select or
specify the primary volume. The rest of the parameters depends on the type of volume (linear or virtual), the user interface used (SMU or CLI),
if the replication is local (using only one array) or remote (using two arrays), and whether or not a remote system is involved and if it has been
added and if it is accessible.

Creating a linear replication set
Choose your link type carefully. The link type of the replication set cannot be changed later. Also, the primary volume does not have to be
created as a master volume. The process of creating the replication set converts a standard volume to a master volume. A secondary volume
created manually must be created as a replication-prepared volume, using the prepare-replication-volume parameter of the create
volume command in the CLI, or by checking the Replication Prepare box on the vdisk’s Provisioning > Create Volume page.

Using the SMU

Note

If creating a remote replication, add the remote system first.

From the volume’s Provisioning > Replicate Volume page, select the secondary system (the local system is the default), and either the vdisk the
secondary volume will automatically be created on or the replication-prepared secondary volume. Then select the link type (FC or iSCSI). Finally,
if you elected to initiate the replication; choose whether to initiate it now or schedule the replication. Allowing the system to automatically create
the secondary volume on the vdisk specified is the easiest and fastest choice for creating a replication set.

Technical white paper Page 21

Figure 7. Creating a linear replication set using the SMU—automatic creation of secondary volume

Using the CLI

Note

If you want a secondary volume created for you on a vdisk on a remote system, you must add the remote system first. Even if you’re using a
replication-prepared volume on a remote system, adding the remote system first makes creating the replication set easier since you don’t have to
provide the address (es) of the ports of the system that contains the secondary volume.

Technical white paper Page 22

Use the create replication-set command, and specify the link-type (optional if supplying the primary-address), the
remote-system (for a remote replication, and if the remote system has previously been added), the remote-vdisk or replication-prepared
remote-volume, the secondary-address (optional for local replications or if the remote system has previously been added), and the
primary-volume.

# create replication-set link-type iSCSI secondary-address ip=10.20.5.170,10.30.5.171 remote-volume dst primary-address
ip=10.20.5.160,10.30.5.161 set src-dst src

Info: The volume was created. (spsrc)
Info: Converted the volume to a master volume. (src)
Info: The primary volume was prepared for replication. (src)
Info: Started adding the secondary volume to the replication set. (dst)
Info: Verifying that the secondary volume was added to the replication set. This may take a couple of minutes... (dst)
Info: The secondary volume was added to the replication set. (dst)
Info: The primary volume is ready for replication. (src)
Success: Command completed successfully.

Command example 3 Creating a linear replication set using the CLI - specifying addresses and secondary volume when management
ports cannot communicate

Creating a virtual replication set
When creating a replication set using a virtual primary volume or volume group, the secondary volume or volume group is created automatically;
you cannot create a secondary volume or volume group manually. If the secondary pool name does not match the primary pool name, specify the
secondary pool name manually.

Note

Create the peer connection that is required as part of the replication set before attempting to create the replication set.

Using the SMU
From the Replications topic, select the peer connection, then select the Create Replication Set action. From the Create Replication Set panel,
provide the Replication Set Name, select Single Volume or Volume Group to display the appropriate choices for the source, select the volume
or volume group to replicate, and modify the Secondary Volume Name and Peer System Pool as desired. Finally chose whether to schedule
replications. Once the replication set has been created, you’ll have a chance to initiate the initial replication if replications were not scheduled.

Technical white paper Page 23

Figure 8. Creating a virtual replication set for a volume from the Replications topic in the SMU

Alternatively, from the Volumes topic, select the volume or a member of the volume group to replicate, then select the Create Replication Set
action. From the Create Replication Set panel, select Single Volume or Volume Group, provide the Replication Set Name, and modify the
Secondary Volume Name and Secondary Pool as desired. Finally chose whether to schedule replications. Once the replication set has been
created, you’ll have a chance to initiate the initial replication if replications were not scheduled.

Technical white paper Page 24

Figure 9. Creating a virtual replication set for a volume group from the Volumes topic in the SMU

Using the CLI
Use the create replication-set command, and specify the peer-connection, primary volume or volume group and replication set name,
at a minimum. You may also choose the name of the remote pool (A or B), and change the remote volume name if replicating a volume rather
than a volume group.

# create replication-set peer-connection PhxSea primary-volume Src secondary-pool B secondary-volume-name Dst SrcDst
Success: Command completed successfully.

Command example 4 Creating a virtual replication set using the CLI

Technical white paper Page 25

Scheduling replications

The scheduler can be used to replicate data from a primary volume in regular intervals to the remote system. Creating a replication schedule
consists of two parts; creating a replication task, which indicates the action of the task (in this case replication) and parameters associated with
the task, and creating a schedule for running the task. The CLI requires two commands to perform this, while the SMU creates the task and
schedule in one operation.

Common schedule parameters
Parameters common to all schedules are the start time and date, which must be a time and date in the future; recurrence or repetition interval—
if not set or selected, the replication will occur only once; end time and date or count limit (the number of times to run the task); and time and date
constraints, which only constrains when the task starts, and is not a window in which the task must complete.

Scheduling a linear replication
Notes on parameters for scheduled linear replication tasks
When a scheduled replication occurs, the name of a replication image (the name of the primary snapshot) created by the scheduled task will
begin with a prefix you specify, followed by “_R” and then a four digit number, starting with 0001; for example, if the prefix was “Data”, the first
replication image will have the name “Data_R0001”.

To control space usage, specify the number of images (replication snapshots) to retain; this is the retention count. The number is the
maximum number—fewer images (snapshots) may be retained due to snapshot space limitations.

There are two replication modes. For one mode, a new snapshot is created and the system will replicate it, for the other, the system will
replicate the most recent snapshot. The second mode is highly useful when another application, such as VSS, performs the actual snapshot
creation.

Using the SMU
Defaults are provided for the Replication image prefix, the Replication Mode and the Replication Images to Retain; change these to suit. See
the Notes on parameters for scheduled linear replication tasks and the Common schedule parameters sections above for more information.

Option 1: Create the schedule while creating the replication set. Check the Initiate Replication box and select the Scheduled radio button.

Technical white paper Page 26

Figure 10. Creating a linear replication schedule when the replication set is created using the SMU

Option 2: Create the schedule for an existing replication set. Select the primary volume’s Provisioning > Replicate Volume page, and select the
Scheduled radio button.

Technical white paper Page 27

Figure 11. Creating a linear replication schedule for an existing replication set using the SMU

Using the CLI
First, create the task. For linear replication tasks, you must specify the task type (Replicate Volume), the source volume, snapshot prefix, and
the retention count. You may specify the replication mode, the default is to take a new snapshot. See the Notes on parameters for scheduled
linear replication tasks section above for more information.

# create task type ReplicateVolume source-volume Data snapshot-prefix Data_image retention-count 3 replication-mode new-
snapshot DataRepTask

Success: Command completed successfully. (DataRepTask) - The task was created.

Command example 5 Creating a linear replication task using the CLI

Technical white paper Page 28

Then, create the schedule. You must provide the task to run and the schedule’s name; while you must also provide a schedule specification,
only the start time is required. See the Common schedule parameters section above for more information. The minimum interval is 30 minutes.

# create schedule schedule-specification "start 2016-02-22 22:00 every 2 hours count 5" task-name DataRepTask DataRepSchedule
Success: Command completed successfully. (DataRepSchedule) - The schedule was created.

Command example 6 Creating a linear replication schedule using the CLI

Scheduling a virtual replication
Using the SMU
While creating the replication set, check the Scheduled box on the Create Replication Set panel, or, after the replication set has been created,
from the Replications topic, select the replication set and select the Schedule Replications action. On the Schedule Replications panel, you must
provide the Task Name. See the Common schedule parameters section above for more information.

Figure 12. Creating a virtual replication schedule using the SMU

Technical white paper Page 29

Using the CLI
First, create the task. For virtual replication tasks, you must specify the task type (Replicate), the replication set name or serial number, and the
task name.

# create task type Replicate Replication-set SrcDst SrcDstTask
Success: Command completed successfully. (SrcDstTask) - The task was created.

Command example 7 Creating a virtual replication task using the CLI

Then, create the schedule. You must provide the task to run and the schedule’s name; while you must also provide a schedule specification,
only the start time is required. See the Common schedule parameters section above for more information. The minimum interval is 60 minutes.

# create schedule schedule-specification "start 2016-02-25 07:00 every 60 minutes only any weekday of year" task-name
SrcDstTask SrcDstSched

Success: Command completed successfully. (SrcDstSchedule) - The schedule was created.

Command example 8 Creating a virtual replication schedule using the CLI

Technical white paper Page 30

Deleting a replication set

The volumes associated with the replication set are not deleted, but are converted or changed to become accessible to hosts. Linear replication
snapshots are converted to standard snapshots. You can only delete linear replication sets from the system that contains the primary volume; you
can delete virtual replication sets from either system.

Deleting a linear replication set using the SMU
Use the primary volume’s Provisioning > Remove Replication Set page.

Figure 13. Deleting a linear replication set using the SMU

Technical white paper Page 31

Deleting a virtual replication set using the SMU
Select the replication set from the Replications topic, then use the Delete Replication Set action.

Figure 14. Deleting a virtual replication set using the SMU

Deleting a replication set using the CLI
For either linear or virtual replications, use the delete replication-set command.

# delete replication-set SrcDst
If you delete the replication set, the primary volume and secondary volume will no longer be in a replication relationship.

Although the data in both volumes will remain unchanged, any future replications from the primary volume must be to a
different secondary volume.
Do you want to continue? (y/n) y
Success: Command completed successfully.

Command example 9 Deleting a replication set using the CLI

Technical white paper Page 32

Accessing the secondary volume’s data

Exporting a replication image of a linear replication volume
To access a secondary linear volume’s data, export one of the replication images (snapshots) to a standard snapshot on the secondary system;
export the last replication image on the secondary volume’s system to effectively access the secondary volume’s current data. This newly created
snapshot can then be mounted and used to verify data or for any other purpose. Any change made in this new snapshot does not affect the
original replication snapshot or secondary volume. Snapshots exported from a replication image count against the snapshot license limits. Use the
replication image’s Provisioning > Export Snapshot page in the SMU or the export snapshot CLI command

.

Figure 15. Exporting a snapshot of a replication image using the SMU

Technical white paper Page 33

# export snapshot name init-snap init
Info: The exported snapshot will reside in the snap pool. If the snap pool reaches its critical threshold, the snapshot may

be deleted, even if it is mapped. To preserve the exported snapshot's data, create a volume copy of the exported snapshot.
Info: The snapshot has been exported. (init-snap)
Success: Command completed successfully.

Command example 10 Exporting a snapshot of a replication image using the CLI

Creating a snapshot of a virtual replication volume
To access a secondary virtual volume’s data, create a snapshot of the secondary volume. This newly created snapshot can then be mounted
and used to verify data or for any other purpose. Any change made in this new snapshot does not affect the secondary volume. Snapshots
made from a secondary volume count against the snapshot license limits. In the SMU, select the secondary volume from the Volumes topic,
then select the Create Snapshots action, or use the create snapshots CLI command.

Figure 16. Creating a snapshot of a replication volume using the SMU

# create snapshots volumes Dst Dst-snap
Info: The virtual pool is overcommitted. Ensure that event notification is configured to receive warnings before running out

of physical storage.
Success: Command completed successfully. (Dst-snap) - Snapshot(s) were created.

Command example 11 Creating a snapshot of a replication volume using the CLI

Technical white paper Page 34

Setting the primary volume (linear replications only)

By default, the source volume is designated as a primary volume and the destination volume is designated as a secondary volume. If any
failure occurs at the local site, the secondary volume on the remote system can be changed to a primary volume (the secondary volume now
appears as a primary volume in the remote system). The result is that this volume now can be mapped and is accessible to hosts. This is
necessary for applications to fail over to the remote site. Once your local site comes up again, you must change the original primary volume to
be a secondary volume for the following reasons:

1. If both the volumes participating in the replication set are primary volumes, replication will not complete.

2. Once the volume at the local system becomes secondary, you can replicate data back from the remote system to the local system. This will
synchronize the two systems.

Since a secondary volume cannot be mapped, unmap a primary volume before changing it to a secondary volume. Once the data is replicated back
to the local system from the remote system, change the local system’s volume to a primary volume and change the remote system’s volume to a
secondary volume. Note that while both volumes can be designated as primary, only one volume in a set can be a secondary volume.

Use the secondary or primary volume’s Provisioning > Set Replication Primary Volume page, or the set replication-primary-volume
command.

Figure 17. Setting the primary volume using the SMU

Technical white paper Page 35

# set replication-primary-volume primary-volume dst volume dst
Info: Started setting the primary volume of the replication set. (src-dst)
Info: Setting the primary volume of the replication set. This may take a couple of minutes... (src-dst)
Info: Successfully set primary volume: (dst)
Info: The primary volume of the replication set was changed. (src-dst)
Success: Command completed successfully.

Command example 12 Setting the primary volume using the CLI

Verifying replication data links

You may want to verify the data link between the local and remote system, or, for linear replications only, the link between ports on the system.

For linear replications, the remote system’s Tools > Check Remote System Link page of the SMU and the verify remote-link command in
the CLI are available to verify the link connectivity between the local and remote systems. This tool should be run before creating a replication set.
Sample outputs of remote system link check in the SMU and CLI are provided here.

Figure 18. Check remote system link output with iSCSI connectivity using the SMU

Technical white paper Page 36

# verify remote-link remote-system KansasCity link-type ALL
Port Type Links
---------------------------------------------
A1 FC
A2 FC
A3 iSCSI A1,B1
A4 iSCSI A2,B2
B1 FC
B2 FC
B3 iSCSI A1,B1
B4 iSCSI A2,B2
---------------------------------------------
Success: Command completed successfully.

Command example 13 Check remote system link CLI output where the remote system is iSCSI only

In the system’s Wizards > Replication Setup Wizard, you can also enable a remote link check by selecting the check box.

Figure 19. Check remote system link in the Replication Setup Wizard of the SMU

Technical white paper Page 37

For virtual replications, use the CLI command show peer-connections with the verify-links parameter to check the data link.

# show peer-connections verify-links PhxSea

Info: This may take a few minutes to ping all port combinations...
Peer Connections

----------------

Peer Connection Name: PhxSea
Peer Connection Type: iSCSI

Connection Status: Online

Health: OK
Health Reason:

Health Recommendation:

Local Port Port Address Reachable Remote Links

------------------------------------------------------------------------------------

A3 10.20.5.168 A1,B1

A4 10.30.5.168 A2,B2

B3 10.20.5.169 A1,B1

B4 10.30.5.169 A2,B2

Remote Port Port Address Reachable Local Links

------------------------------------------------------------------------------------

A1 10.20.5.162 A3,B3

A2 10.30.5.162 A4,B4

B1 10.20.5.163 A3,B3

B2 10.30.5.163 A4,B4

Success: Command completed successfully.
Command example 14 Verify links for a peer connection for virtual replications using the CLI

Technical white paper Page 38

To check links between ports for a local linear replications from the SMU use the system’s Tools > Check Local System Link and the CLI by

running the command verify links. This will check links from controller A ports to controller B ports irrespective of where you run the
command from (e.g., controller A or B).

Figure 20. Check Local System Link using the SMU

Technical white paper Page 39

# verify links
Port Type Links
---------------------------------------------
A1 FC B1
A2 FC B2
A3 iSCSI B3
A4 iSCSI B4
B1 FC A1
B2 FC A2
B3 iSCSI A3
B4 iSCSI A4
---------------------------------------------
Success: Command completed successfully.

Command example 15 Check local link using the CLI

In the CLI, you can use the same command to check remote system links for replication purposes; this tests the links to be used for replication
from one system to another system.

In the system’s Wizards > Replication Setup Wizard, you can also enable a local link check by selecting the check box.

Figure 21. Check local link in the Replication Setup Wizard of the SMU

Technical white paper Page 40

Ports connected for replication

Connected port field in a linear replication set
For a remote primary or secondary volume, the Connected Ports field of the Replication Addresses table of the volume’s View > Overview
page shows the IDs of up to two ports from the remote array that are connected to ports in the local array. If two ports are connected but only
one is shown, this could mean that a problem is preventing half the available bandwidth from being used.

Note

This field shows N/A for a local primary or secondary volume.

Figure 22. Connected ports being used for a linear replication using the SMU

Technical white paper Page 41

For the CLI, use the show replication-sets command.

# show replication-sets rsFSDATA

Replication Set [Name (rsFSDATA) Serial Number (00c0ffda02f30000b857ab5601000000) ] Primary Volume:

Name Serial Number Status Status-Reason Monitor Location Primary-Volume Primary-Volume-Serial

Primary-Volume-Status MaxQueue MaxRetryTime On Error Link Type On Collision Monitor Interval Priority Connection Status

Connection Time

--------------------------------------------------------------------------------------------------------------------------

-------

FSDATA 00c0ffda02f300007956ab5601000000 Online N/A OK Local FSDATA

00c0ffda02f300007956ab5601000000

Online 32 1800 Retry iSCSI Oldest 300 Medium Not Attempted

N/A

Connected Ports Remote Address

--------------------------------------------------------------

N/A IP=10.20.5.160:3260

N/A IP=10.30.5.160:3260

N/A IP=10.20.5.161:3260

N/A IP=10.30.5.161:3260

rFSDATA 00c0ffdadd5c0000a849ab5601000000 Online N/A OK Remote FSDATA

00c0ffda02f300007956ab5601000000

Online 32 1800 Retry iSCSI Oldest 300 Medium Online

2016-02-25 08:52:46

Connected Ports Remote Address

--------------------------------------------------------------

A3 IP=10.20.5.170:3260

A4 IP=10.30.5.170:3260

A3 IP=10.20.5.171:3260

A4 IP=10.30.5.171:3260

Success: Command completed successfully.
Command example 16 Showing connected ports for a linear replication using the CLI

Technical white paper Page 42

Connected ports listed for a peer connection for virtual replications
Hover over the peer connection in the Replication tab to see the ports connected for the peer connection.

Figure 23. Connected ports used in a peer connection for virtual replications using the SMU

Technical white paper Page 43

For the CLI, use the show peer-connections command.

# show peer-connections

Peer Connections
----------------

Peer Connection Name: PhxSea

Peer Connection Type: iSCSI
Connection Status: Online

Health: OK

Health Reason:
Health Recommendation:

Local Port Port Address

----------------------------------------------------------

A3 10.20.5.168

A4 10.30.5.168

B3 10.20.5.169

B4 10.30.5.169

Remote Port Port Address
----------------------------------------------------------
A1 10.20.5.162
A2 10.30.5.162
B1 10.20.5.163
B2 10.30.5.163

Success: Command completed successfully.

Command example 17 Showing connected ports for a peer connection for virtual replications using the CLI

CHAP settings and Remote Snap

If you configure CHAP with Remote Snap, you can use CHAP to authenticate iSCSI login requests between the local system and a remote
system:

• Create a one-way CHAP record on each system. On the local system, the CHAP record must refer to the node name of the remote system.
On the remote system, the CHAP record must refer to the node name of the local system. Both records must use the same secret.

Use the create chap-record command to create a CHAP record:

# create chap-record name iqn.1991-05.com.microsoft:myhost.domain secret 0D12x

Command example 18 Creating a CHAP record using the CLI

• After the CHAP records are created, enable CHAP on the primary system, the secondary system, or both.
To enable CHAP, use the set iscsi-parameters command:

# set iscsi-parameters chap enabled
Command example 19 Enabling CHAP using the CLI

Technical white paper Page 44

Table 1. CHAP settings and corresponding behavior with Remote Snap

LOCAL SYSTEM REMOTE SYSTEM EXPECTED BEHAVIOR

CHAP Disabled (Secret: No; CHAP record: No) CHAP Disabled (Secret: No; CHAP record: No) Remote Snap works fine.
No iSCSI authentication
CHAP Enabled (Secret: SECRET1; CHAP record: Yes) CHAP Enabled (Secret: SECRET1; CHAP record: Yes)
CHAP Enabled (Secret: SECRET1; CHAP record: Yes) CHAP Enabled (Secret: SECRET2; CHAP record: Yes) Remote Snap works fine.

CHAP Enabled (Secret: No; CHAP record: No) CHAP Enabled (Secret: No; CHAP record: No) Remote Snap will fail. Use the same secret for
both the local and remote systems.
CHAP Disabled (Secret: SECRET1; CHAP record: Yes) CHAP Enabled (Secret: SECRET1; CHAP record: Yes)
CHAP Disabled (Secret: SECRET1; CHAP record: Yes) CHAP Enabled (Secret: SECRET2; CHAP record: Yes) Remote Snap will fail. Enabling CHAP without
specifying a secret for an iSCSI initiator
effectively blocks that initiator.

Remote Snap works fine.

Remote Snap will fail. Use the same secret for
both the local and remote systems.

Note

If you are performing a local replication involving iSCSI ports, CHAP will not be used.

Disabling or enabling CHAP will cause the host ports to reset. If the CHAP records are not configured correctly (see Table 1 CHAP settings and
corresponding behavior with Remote Snap table above), then replication cannot occur.

Technical white paper Page 45

Examples of replication types and operations

Remote replication

See the following for an illustration of remote replication.

Standard Remote Replication

Application Alternate
Server Server

I/O Path Management I/O Path
Network
Local Remote
Array Replication Connection Topology Array

Primary I/O Path Secondary
Volume FC or iSCSI Volume

The time for the initial replication
depends on the size or allocated space of the
source volume and connection speed.

First Initial replication can be started using Initiate Replication
replication in the SMU, or when creating a virtual replication set by
checking the Scheduled box or selecting Yes at the end
image of the replication set creation.

1 2
Use SMU Replication Setup Wizard Customer can issue more linear replication
to create a linear replication set commands prior to completion of first
with local and remote arrays. replication.

Figure 24. Illustration of remote replication

Using FC
You can set up local and remote sites connected via an FC network and can have linear replication sets performing replications over FC. This is
useful in cases where local and remote sites are in different blocks of a campus or building.

FC ports can be used to transfer regular data while they are being used for replication. However, this action will result in decreased performance for
both the data path and the replication transfer.

Using iSCSI
When the local and remote systems are in different geographical regions, you can create replication sets using iSCSI to perform replications over a
WAN. For example, when the local system is in New York and you are planning to set up your backup system (remote system) in Houston, you can
create remote replication sets using iSCSI as the transfer media for performing replications.

For linear replications, perform a physical media transfer to overcome bandwidth and latency issues with the initial replication. These issues
can sometimes be caused by a large amount of data in the primary volume getting replicated to a remote system. (See more on these issues in
the Physical Media Transfer section above.)

Technical white paper Page 46

For virtual replications, you may want to co-locate the systems to overcome bandwidth and latency limitations of a WAN. However, since only
allocated data is transferred, network limitations may be acceptable when the systems are dispersed geographically.

If you are running firmware older than T230 on a P2000 G3, host I/O and replication should not be done at the same time on an iSCSI port.

Local replication and Physical Media Transfer (for linear replications only)

See the following for an illustration of local replication and physical media transfer, resulting in a remote replication.

Local Replication and Physical Media Transfer Alternate
Server
Application
Server

I/O Path Management Perform “Physical I/O Path
Network Media Transfer”
Local of drives or enclosure
Array
I/O Path I/O Path Remote
FC or iSCSI Array

Secondary
Volume

Use SMU Replication Perform “detach” operation Perform “Stop” operation
Wizard to create a on secondary volume on vdisk whicn contains
replication set on same the secondary volume
storage array, use
separate vDisks Physically add drives or Secondary volume
and drives enclosure to array. is not yet part of the
replication set!
Now more replication commands can
be performed on the replication Set. Primary “Start” vdisk that contains
Volume the secondary volume

When replication link is established, Secondary volme
use “reattach” operation to pair the is now part of the
local array and remote array volumes replilaction set!
to re-establish the Replication Set.
Secondary Volume

Initial replication synch point set
is the physical media transfer

First replication image First replication image

Figure 25. Illustration of local replication and physical media transfer

Important notes on Physical Media Transfer
• If you intend to move a disk drive enclosure, add the enclosure at the end of the chain of connected enclosures.

• Make sure that the remote system supports the chosen link type (iSCSI or FC); the link type can’t be changed once the replication set has
been created.

• Make it possible to perform the physical media transfer by setting up a local replication such that the secondary volume resides on one of
the following:

– On the same array, but on different vdisks (so that disks can be removed and physically transferred to the remote site).

– In an attached drive enclosure. This drive enclosure will be attached to a remote system later.

• When using Full Disk Encryption (FDE) on an MSA 2040 Storage array, it is a best practice to move media between systems that are
identically configured with FDE enabled or disabled. That is, move secured Self-Encrypting Drives (SED) to a secured FDE system, and
unsecured SEDs or non-SEDs to an unsecured FDE system or non-FDE system.

Technical white paper Page 47

Detailed steps for Physical Media Transfer
1. Ensure the first, initial, replication is complete

2. Detach the secondary volume, which resides on the local system. If the secondary volume’s vdisk contains any other secondary volumes,
detach those volumes also. Use the detach replication-volume command via the CLI or the secondary volume’s Provisioning >
Detach Replication Volume function in the SMU.

• You must detach the replication volume before moving the secondary volume to the remote system.
• Once the secondary volume is detached it remains part of the replication set but is not updated with any new data.

3. Ensure the detach operation is complete.

4. Stop the secondary volume’s vdisk and associated snap pool’s vdisk (if the secondary volume and its snap pool reside on separate vdisks)
using the stop vdisk command in the CLI or using the vdisk’s Provisioning > Stop vdisk function in the SMU.

5. If moving a drive enclosure, power off the enclosure. If moving only the disks there is no need to power off the enclosure. After the drive
enclosure is powered off, there may be unwritable cache data in the drive enclosure. Use the clear cache command in the CLI to clear
the unwritable cache.

6. Remove the disks or enclosure containing the disks and attach or move them into the remote system.

• You should power down an enclosure before inserting disks.
7. If the secondary volume’s snap-pools are on a different vdisk from the volume itself, start the snap pool’s vdisk using the start vdisk

command in CLI or the vdisk’s Provisioning > Start vdisk function in the SMU.
8. Start the secondary volume’s vdisks. The secondary volume appears on the system at the remote site.

9. Reattach the secondary volume to add it back to the set. This operation makes the secondary volume a part of the original set. Use the
reattach replication-volume command or the volume’s Provisioning > Reattach Replication Volume page in the SMU.

10. Continue replicating from the local site.

Disaster recovery operations

If the local site fails, the applications need to switch to the remote site.

Linear replications
To bring up the remote site, do the following:

1. Convert the remote volume (secondary volume) to a primary volume using the set replication-primary-volume CLI command or
by selecting the secondary volume’s Provisioning > Set Replication Primary Volume function from the SMU.

– During the conversion to a primary volume, the volume is rolled back, or synced, to a replication snapshot. By default, the volume syncs to
the latest replication snapshot, but you can choose any of the previous replication snapshots.

– Any data that has not been replicated is lost.

– A secondary volume can be converted to a primary via the SMU or CLI.
2. Map the new primary volume, which resides on the remote site, to a LUN and use as you would use the original primary volume.

Switch the applications to this new primary volume and continue using the applications.

Once the failure has been addressed at the local site, complete the following steps:

1. Make the original primary volume a secondary volume using the set replication-primary-volume CLI command or by selecting
the volume’s Provisioning > Set Replication Primary Volume function from the SMU.

Important

A secondary volume cannot be mapped, so be sure to unmap the original primary volume before attempting to make it a secondary volume.

Technical white paper Page 48

2. Replicate any data written to the remote volume (now acting as primary volume residing at remote system) to the volume residing at the
local system (now acting as secondary volume). This can be performed in a single replication or in multiple replications. This ensures that
all data has been transferred properly.

After all the data is replicated back to the local site, convert the volume at the local site to the primary volume and then convert the remote
volume to the secondary volume.

– To convert a primary volume to a secondary volume, set the other volume of the replication set as the primary—perform this operation
on both systems. You can perform this operation using the CLI command set replication-primary-volume or using the SMU via
the volume’s Provisioning > Set Replication Primary Volume function.

Re-establish the replication set to the remote site. Continue using the scheduler for running remote replications in regular intervals.

Failover to remote site

Application Application swi tches to Alternate
Server remote site and acc ess the Server
primary volume
I/O Path I/O Path

Management Remote
Network Array

Replication Connection Topology

Local I/O Path
Array FC or iSCSI

Primary Volume Primary Volume

No replication happening now

Primary volume no Initial replication synch point set Secondary volume
longer acc essible to is created with “initiate replication” converted to
user primary volume

First replication image

Latest replication image

Latest replication image

Technical white paper Page 49

Faiback to local site

Application Pause the application so that Alternate
Server new data will get replicated Server
back to local site
I/O Path

Management I/O Path
Network

Replication Connection Topology

Local I/O Path Remote
Array FC or iSCSI Array

Secondary Volume Primary Volume

Primary volume Initial replication synch point set
converted to is created with “initi ate replication”
secondary volume

First replication image

Older replication image Older replication images Initiate replication
Latest replication image
Primary Volume Latest replication image Secondary Volume
Primary volume
Application switch converted to
to local site and secondary volume
continues operation

Secondary volume Initial replication synch point set
converted to is created with “initi ate replication”
primary volume

Older replication images

Older replication images

Latest replication images

User continues
replication

Figure 26. Disaster recovery operations for linear replications

Technical white paper Page 50

Virtual replications
To bring up the remote site, consider that the secondary volume cannot be mapped, you cannot reverse direction of the replication set, and a
snapshot can be the primary volume of a replication set. Once at least one replication has completed, to allow access to the secondary volume’s
data, you can either delete the replication set, which will remove the secondary volume from the replication set and convert it to a standard base
volume, or create a snapshot of the secondary volume and access the snapshot rather than the volume itself. If the replication set is deleted, the
only way to include the volume that was a secondary volume into a replication set is to create a new replication set with the volume as the primary,
or source, volume.

The preferred method that provides the most flexibility is to create two snapshots of the secondary volume—one that is mapped read-write to
hosts and is intended for modification of the data, and one that, regardless of the type of mapping (read-only or read-write), is not to be modified.

Figure 27. Virtual replication failover to remote site