Tuesday, 3 January 2017

Part 3: Recover A VM Using vSphere Replication

Part 2: Pairing vR Sites and configuring replication for a virtual machine

In this article, we will be performing a recovery of replicated virtual machine using vSphere replication. To perform a recovery, you will have to select the target vCenter (vCenter-DR in my case), select Monitor and Incoming replication.

You will see the below screen at this point and you will notice a big red button with a play symbol. This would be the recovery option. Select this icon.

You will then be presented with the type of recovery you would like to do

Recover with recent changes: This first option will need to have the source VM powered down. Before initiating the recovery process it will sync the recent changes with the source VM, so the recovered VM will be up-to-date.

Use latest available data: If you would not like to power down the source or if the source is unavailable or corrupted, you will choose this option. Here, it will make use of the recent replicated data to recover the virtual machine.

We will be using the second option to recover the virtual machine. In this wizard you will have to choose a destination folder to restore this virtual machine to.

You will then have to select the ESXi host and (if available) a resource pool to recover this virtual machine to.

You will have an option to keep the recovered VM Powered on or off. Depending on your requirement you can select this, and click Finish to begin the recovery process.

Once the recovery is complete, the virtual machine will be now available in the target site, and all the VM files that were named as hbr.UUID.vmdk (VM files that were replicated) will be renamed to the actual virtual machine files)

The status of the replication will now switch to Recovered and there will be no more active replication for this virtual machine.

Resuming Replication After Replication: Reprotect and Failback.

In most scenarios, once a VM is recovered you would like to re-establish the replication the other way to ensure there is a new replicated instance in case if this recovered virtual machine fails at some point. This is called as reverse replication or reprotection.

Initially, the replication was from vcenter-prod to vcenter-dr with the virtual machine residing on the vcenter-prod. Post a recovery, the virtual machine is now running on vcenter-dr. So, now the replication direction changes from vcenter-dr to vcenter-prod.

You will have to first stop the current configured replication for the virtual machine. On the target site, under incoming replication (Above screenshot), right click the VM with status as recovered and select Stop. Then, the virtual machine on the source has to be unregistered (Remove from inventory) on the source side. Once the replication is stopped and the source (old) virtual machine is unregistered, you will then have to reconfigure the replication. The process is same as discussed in Part 2 of this article.

The only difference is, when you select a destination datastore for the replication data to reside you will receive the following message. Select Use Existing. With this option, it will inform you that there are already a set of drives available on the target site and they will be the replication seeds. A initial Full Sync will still occur, but it will not be a copy of data, it will be just a check of the hash to ensure the validity. Once this is done, the new data will then be replicated first, and then replicated according to your set RPO.

Once the replication status goes to OK, you will have a valid replicated instance of the virtual machine at the new target site ready to be recovered.

Performing A Manual Recovery.

Until now, you saw vSphere Replication taking care of all recovery operation. But for some reason, the vCenter is down and you would like to recover a critical virtual machine. If vCenter is down, you cannot manage your vSphere Replication. Then in this case, we will be performing a manual recovery.

From the SSH of the ESXi host, you can see the VM files that are replicated:
# cd /vmfs/volumes/54ed030d-cd8f4a16-9fef-ac162d7a2fa0/Router

-rw-------    1 root     root        8.5K Jan  3 08:24 hbrcfg.GID-c3732b6f-de63-4c55-a830-a4437d91a143.4.nvram.8
-rw-------    1 root     root        3.1K Jan  3 08:24 hbrcfg.GID-c3732b6f-de63-4c55-a830-a4437d91a143.4.vmx.7
-rw-------    1 root     root       84.0K Jan  3 08:24 hbrdisk.RDID-297047a6-c7d0-4322-b290-bb610582daf1.5.59562057314158-delta.vmdk
-rw-------    1 root     root         368 Jan  3 08:24 hbrdisk.RDID-297047a6-c7d0-4322-b290-bb610582daf1.5.59562057314158.vmdk
You will have to rename these VM files to vmdk, flat.vmdk, vmx, nvram extensions. So, create a new folder under the datastore directory.
# cd /vmfs/volumes/54ed030d-cd8f4a16-9fef-ac162d7a2fa0/
# mkdir Rec
Pause the replication and copy / clone the vmdk to the new location using vmkfstools -i
# cd /vmfs/volumes/54ed030d-cd8f4a16-9fef-ac162d7a2fa0/Router
# vmkfstools -i hbrdisk.RDID-297047a6-c7d0-4322-b290-bb610582daf1.5.59562057314158.vmdk -d thin /vmfs/volumes/54ed030d-cd8f4a16-9fef-ac162d7a2fa0/Rec/Rec.vmdk
You will see the following output:
Destination disk format: VMFS thin-provisioned
Cloning disk 'hbrdisk.RDID-297047a6-c7d0-4322-b290-bb610582daf1.5.59562057314158.vmdk'...
Clone: 100% done.

Copy / Rename the vmx and nvram files using the below command:
# cp -a hbrcfg.GID-c3732b6f-de63-4c55-a830-a4437d91a143.4.vmx.7 /vmfs/volumes/54ed030d-cd8f4a16-
# cp -a hbrcfg.GID-c3732b6f-de63-4c55-a830-a4437d91a143.4.nvram.8 /vmfs/volumes/54ed030d-cd8f4a1
Finally, register the VM from the command line using:
# vim-cmd solo/registervm /vmfs/volumes/54ed030d-cd8f4a16-9fef-ac162d7a2fa0/Rec/Rec.vmx
If the registration was successful there will be a VM ID allocated as the output and you can verify the same in the vSphere client.

That's pretty much it.


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