Dell Unity™ Family Unisphere® Command Line Interface User Guide

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Create replication sessions

Ensure you have completed the necessary configuration tasks before creating a replication session.

For asynchronous replication, you can replicate existing snapshots and snapshots that are created from snapshot schedules.

For synchronous file replication, you cannot replicate existing snapshots or snapshots that are created from snapshot schedules.

NOTE:Snapshots that have been created and attached as well as read/write (share) snapshots (as opposed to read-only checkpoint snapshots) are not eligible for replication. Only unattached (read-only) snapshots are eligible for replication.

The following conditions apply to snapshot replication:

  • Asynchronous replication: You can replicate existing snapshots and snapshots that are created from snapshot schedules.
  • Synchronous file replication: You cannot replicate existing snapshots or snapshots that are created from snapshot schedules. You can only replicate those snapshots and snapshots that are created from snapshot schedules after you have established the synchronous replication session and it is Active.
NOTE: On a NAS server protected by replication, you must create a replication session for each file system on it. Otherwise, file system-related configurations like shares and exports may be lost after a NAS server replication session failover.

Performing a snapshot replication from a source system running OE version 4.0, 4.1, 4.2, 4.3, or 4.4 to a destination system running OE version 5.x requires upgrading the source system to OE version 4.5 first. Upgrading to OE version 4.5 is not required but recommended if you want to perform LUN or file system replication from OE version 4.0, 4.1, 4.2, 4.3, or 4.4 to OE version 5.0 without any snapshot replication.

Prerequisites

Before creating a replication session, complete the following configuration tasks:

  • Create the storage resource that provides the replication source.
  • For local replication, create a replication destination on a local system.
  • For remote replication, create a replication connection to a remote system, and create a replication destination on that remote system.
  • For asynchronous replication in a co-existing asynchronous and synchronous replication with one source resource topology, create the asynchronous replication destination NAS server with both the -replDest and the -backupOnly attributes set to yes. These attributes must be set to yes on the asynchronous replication destination NAS server when the source NAS server is synchronous-replicated; otherwise, the asynchronous replication session cannot be created.

Format

/prot/rep/session create [-async] -srcRes <value> [-srcSPAInterface <value>] [-srcSPBInterface <value>] –dstType {local | remote –dstSys <value>} -dstRes <value> [-dstSPAInterface <value>] [-dstSPBInterface <value>] [-name <value>] [-elementPairs <value>] -syncType {manual [-autoInitiate {yes | no}] | auto [-rpo <value>]} [-replicateHourlySnaps {yes [{-keepSameAsSource | -keepFor <value> | -allowAutoDelete}] | no}] [-replicateDailySnaps {yes [{-keepSameAsSource | -keepFor <value> | -allowAutoDelete}] | no}] [-replicateExistingSnaps] [-allowAsyncSnapReplication {yes | no}] [enableUserSnapCommonBase {-autosearch | -srcCommonBaseSnap <value> -dstCommonBaseSnap <value> [-skipSnapSignatureCheck]}]

Action qualifiers

QualifierDescription
-asyncRun an action in asynchronous mode.
-srcResType the ID of the storage resource to use as the source.
-srcSPAInterface Type the ID of the interface on the SPA of the source system for the replication.
NOTE:This qualifier is used for asynchronous replications on remote systems only. If the qualifier is not specified, the system identifies the interface automatically.
-srcSPBInterface Type the ID of the interface on the SPB of the source system for the replication.
NOTE:This qualifier is used for asynchronous replications on remote systems only. If the qualifier is not specified, the system identifies the interface automatically.
-dstType Specify the type of destination. Valid values are:
  • local—Maintain a full copy of the storage resource on the local system. This has advantages over snapshots in that a full copy, not just a copy of changes, is retained.
  • remote—Maintain a full copy of the storage resource on a remote system by transferring the data over the network.
Remote replication is often used to ensure that a copy is available at a remote site if there is catastrophic data loss, for example, due to natural disaster at the local site.
-dstSysFor remote replication, type the ID of the destination system. View settings for remote storage systems explains how to view the IDs of the remote system configuration on the local system.
-dstResType the ID of the destination storage resource.
-dstSPAInterface Type the ID of the interface on the SPA of the destination system for the replication.
NOTE:This qualifier is used for asynchronous replications on remote systems only. If the qualifier is not specified, the system identifies the interface automatically.
-dstSPBInterface Type the ID of the interface on the SPB of the destination system for the replication.
NOTE:This qualifier is used for asynchronous replications on remote systems only. If the qualifier is not specified, the system identifies the interface automatically.
-syncType This parameter indicates whether to perform the first replication sync (a full sync) automatically. The following example shows the manual option used for the first replication sync: -syncType {manual [-autoInitiate {yes | no}] | auto [-rpo <value>}

Valid values are:

  • manual—Data is replicated when manually initiated.
  • -autoInitiate—The values are for -autoInitiate are as follows:
    • yes enables automatic synchronization.
    • no disables automatic synchronization.
  • auto [-rpo <value>]—Data is replicated automatically in order to maintain the wanted Recovery Point Objective (RPO).
NOTE:This qualifier is used for asynchronous replications only.

As the RPO increases, the potential for data loss also increases, and the amount of required protection space. Lowering the RPO reduces the amount of potential data loss, but also increases network traffic and may negatively impact performance. The default RPO is one hour.

-autoInitiate Specify whether the system performs the first replication synchronization automatically. Valid values are:
  • yes
  • no
NOTE:This qualifier is used for asynchronous replications only.
-rpo Type the time interval for when the synchronization runs. Use the following format:

<HH>[:MM]

Where:
  • HH—Type the number of hours. Range is 00-24 hours (1 day).
  • MM—Type the number of minutes, in 5 minute increments. Range is 05 to 55.
For synchronous replication, specify the value 0. Once it is set, the value cannot be reset from zero to nonzero or from nonzero to zero.
-replicateHourlySnapsSpecify whether to mark hourly scheduled snapshots for replication. Valid values are:
  • yes
  • no
NOTE:This qualifier is used for asynchronous replications only.
-replicateDailySnapsSpecify whether to mark daily scheduled snapshots for replication. Valid values are:
  • yes
  • no
NOTE:This qualifier is used for asynchronous replications only.
-keepSameAsSource Indicate whether to use the same retention policy (expiration time and auto-delete) of the source for the destination. This option propagates changes that are made to the source retention policy to the destination retention policy (from that point forward for newly created scheduled snapshots, old snapshots are left as is). No values are allowed.

This option is enabled by default if -keepFor or -allowAutoDelete are not set.

NOTE:This qualifier is used for asynchronous replications only.
-keepFor Specifies the retention time after which the snapshot is deleted on the destination. The interval can be defined in days or hours. Use the following format:

<value><qualifier>

Where:
  • value—An integer value. If the qualifier is h (hours), the valid range is from 1 to 42840. If the qualifier is d (days), the valid range is from 1 to 1785.
  • qualifier—A value qualifier. The valid values are:
    • h (hours)
    • d (days)
NOTE:This qualifier is used for asynchronous replications only.
-allowAutoDeleteSpecify whether auto delete is allowed on the replicated copy of this snapshot or snapshot set.
NOTE:This qualifier is used for asynchronous replications only.
-replicateExistingSnapsIndicates whether to replicate snapshots that exist on the source resource. This qualifier is a one-time option available during session creation that replicates snapshots existing on the source at that moment in time.
NOTE:This qualifier is used for asynchronous replications only.

Only the user snapshots that are created after the common base snapshots were established and are in the Idle or Pending state are replicated.

All eligible snapshots are replicated with the source retention policy applied for the destination retention policy. For a snapshot to be eligible for this option, it must meet these 3 criteria:
  • The snapshot is created by either the user or a snapshot schedule.
  • The snapshot is read-only (file resource snapshot must be a checkpoint snapshot; block resource snapshot must not be attached).
  • The snapshot is not currently undergoing deletion.
-allowAsyncSnapReplicationIndicate whether snapshot replication is allowed in an asynchronous session. Valid values are:
  • yes
  • no
NOTE:This qualifier is used for file system asynchronous replications only.
-enableUserSnapCommonBaseDesignate the user snapshot as the common base for Unity systems running OE version 5.1.

If this qualifier is absent, the system does not treat the user snapshot as the common base.

NOTE:This qualifier must be set when the replication session is configured.
-srcCommonBaseSnapSpecify the user snapshot identifier that is used as the common base on the source resource for Unity systems running OE version 5.1.
-dstCommonBaseSnapSpecify the user snapshot identifier that is used as the common base on the destination resource for Unity systems running OE version 5.1.
-autosearchEnable the system to perform an automatic search to find a user snapshot that can be used as a common base for Unity systems running OE version 5.1.

If this qualifier is not included, the -autosearch function is disabled.

NOTE:This qualifier must be set when the replication session is configured if you want to avoid a full copy after a failover.
-skipSnapSignatureCheckIndicate whether you want to skip the user snap signature check when using the user snapshot as the common base for Unity systems running OE version 5.1. This qualifier is valid only when specifying the source and destination user snapshots as the common base.
NOTE:Check if the user snapshots are qualified as a common base.
-cascadeReplicatedSnapIndicates whether you want to automatically replicate snapshots downstream when the snapshot is replicated from the inbound replication session.

The valid values are as follows:

  • yes
  • no (default)
-overwriteDestination Indicate whether to overwrite dirty data on the destination; it takes more time to complete full data transfer. If this qualifier is not specified, the destination might contain different data than the source if the destination has corrupted data.

Example

The following command creates a replication session with these settings:

  • Source storage resource is file system RS_1.
  • Destination system type is remote.
  • Remote destination system is RS_2.
  • Remote storage resource is file system LUN_2.
  • Synchronization type is automatic.
  • RPO is 2 hours and 30 minutes.
uemcli -d 10.0.0.1 -u Local/joe -p MyPassword456! /prot/rep/session create -name REP1 -srcRes RS_1 –dstType remote -dstSys RS_2 –dstRes LUN_2 –syncType auto –rpo 02h30m 
Storage system address: 10.0.0.1
Storage system port: 443
HTTPS connection

ID = 81604378625_FCNCH097274B3A_0000_81604378627_FCNCH097274B37_0000
Operation completed successfully.
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