SRM w/Array Based Replication VM LUN Placement

[PeteHow]

If you're using array based replication with SRM does that mean that all VM's you place on a LUN have to be part of a recovery plan?

Also, when you re-protect is the data still on the original LUN or does that get blown away (assuming nothing major happened to the SAN) and need to be completely replicated or is it still there and you push changes to it?  Does that also mean you change the direction of the replication at the SAN level.  Reprotect and make the original site the primary and change the replication back again?

[basher · Accepted solution]

The short answer is yes.

If you're using array based replication with SRM does that mean that all VM's you place on a LUN have to be part of a recovery plan?

Yes, with SANs the unit of replication is the entire LUN. SRM cannot recover individual VMs on a LUN, it needs to recover all of them (for the sake of consistency).

Also, when you re-protect is the data still on the original LUN or does that get blown away (assuming nothing major happened to the SAN) and need to be completely replicated or is it still there and you push changes to it? Does that also mean you change the direction of the replication at the SAN level.  Reprotect and make the original site the primary and change the replication back again?

Re-protect operation in SRM does indeed reverse the replication at SAN level. Making a step back, the failover operation moves all VMs on a LUN from the production to the DR site. If the production site is still up, SRM will cleanly shut down all the VMs and force the SAN to synchronize these changes.Then it will reconfigure the VMs at the production site so they can no longer be powered on. Now that the VMs are the DR site and VMs at the production site are "disabled", it is safe to reverse the replicaton and overwrite the LUN at the original production site.

[PeteHow]

Thanks Stefan.  So when you decide to re-protect is it SRM with the san plugin that tells the SAN to reverse the replication?  Or do we need to engage the SAN team to do that?

Thanks again!

[vbrowncoat]

This is one of the things the SRA (storage replication adaptor) does. It handles communication with the array and handles all the array-side operations. Changes should not need to be made directly on the array.