EMC Unity – Native Asynchronous Block Replication

Question

EMC Unity systems provide synchronous and asynchronous replication solutions which allow you to replicate data locally within the same system, or to other systems, whether they are located at the same site or a remote facility. Having remote replicas of data protects you against outages on the main system, and allows you to recover quickly and easily on a destination system with minimal to no data loss depending on the replication method selected. Note: In EMC Unity, Asynchronous Replication is supported on all Unity Systems. The supported systems include the Unity All Flash models, the Unity Hybrid models, and the UnityVSA. For all systems, Asynchronous Replication comes with all systems at no additional cost. Synchronous Block Replication is only supported on physical Unity Systems. The supported systems include the Unity All Flash models, and the Unity Hybrid models. For EMC Unity All Flash and Hybrid systems, Synchronous Block Replication comes with all systems at no additional cost. In this demonstration, I will setup Native Asynchronous Block Replication in EMC UnityVSA, the configuration for this demonstration as below. Production Array – EMC UnityVSA (Virtual Storage Appliance) Management Network: 10.2.2.160 iSCSI-P1: 10.2.2.161 iSCSI-P2: 10.2.2.162 Remote Array – EMC DR-UnityVSA (Virtual Storage Appliance) Management Network: 10.2.2.170 iSCSI-P1: 10.2.2.171 iSCSI-P2: 10.2.2.172 Step1: Create the replication network on UnityVSA and DR-UnityVSA. In this demo, I will create two replication connections on each Unity Array. Step2: Create the management connection between UnityVSA and DR-UnityVSA. Step3: Create the replication session and select replication mode (Asynchronous) on the source LUN. Step4: Click 'Sync' button to start the Asynchronous Replication session. The four simple steps to complete this replication configuration in EMC Unity.

xKinAnx · Answer

Dear Victor, I replicate one LUN with remote async. And cannot mount the destination LUN. Please explain it help me. My host is Windows Server. Thanks,

DELL_ChrisHolloway · Answer

Assuming you want to carry on replicating whilst you access the destination LUN, then the best way of doing this is to take either a snapshot of the destination LUN or a thin clone.  That can then be mounted on your host on the DR site.

AfrinDange · Answer

Hi ,

I have 2 UnityVSA configured, SourceVSA and DestVSA.

I have created a LUN (lun_1) on sourceVSA and have configured async replication session of it on DestVSA.

I created a snapshot on lun_1 on DestVSA.

I want to perform a Restore operation from snapshot at DestVSA to lun_1 at DestVSA.

But when i select snapshot at DestVSA , and click on More Action, restore option is in grey. i am unable to perform restore of remote snapshot to remote storage lun.

Is there a limitation of Dellemc unity for restore of remote snapshot to remote storage lun. or Its limitation of Unity VSA.

Unity VSA(os vesion) is 5.0.0.0.5.116

Any information would be highly appreciable.

DELL_ChrisHolloway · Answer

I'm pretty sure in this scenario you would need to break the replication relationship in order to do a snap restore on the destination LUN.

What's the specific use case you want to achieve with restoring a snapshot on to a replication destination?

AfrinDange · Answer

Hi Chris,

Thanks for your reply.

Whats the procedure to perform break of replica relationship.

In replication session there is no option for break.

possible options are Pause, Delete, Sync, Failover with Sync.

- Also if i break how to reestablish the relationship again.

Our use case is if our source array is down and we want to use remote source volume, we wish to restore the snapshot present at remote array to remote source volume.

DELL_ChrisHolloway · Answer

In the scenario you describe, where the source array has failed, you would perform a failover from the destination (this is called an unplanned failover). After the failover, you will be able to restore snapshots to the destination LUN if required.

You can find more details about failover, failback, resume and so on in the Replication Technologies white paper: https://www.dellemc.com/resources/en-us/asset/white-papers/products/storage/h15088-dell_emc_unity-replication_technologies.pdf

akfd · Answer

Hi,

@ChrisHolloway I have created a snapshot of replicated target lun and I want to overwrite this snapshot on another attached standalone lun, how do I do it?

Also, the array user that I am using shows the restore option in gray in the snapshot tab of a replicated lun. Is it true that restore operation cannot be performed in this type of replicated environment?

What are the use-cases in which I can use the utility of restore operation?

Many thanks.

Unity

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