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TedH256
Expert
Expert
‎11-20-2015 08:29 AM

SRM with array based replication - how to achieve better than crash consistency?

So I believe that when using SRM with vSphere replication, that when VMs are replicated, VMware tools first does a VSS quiesce on the VM. We can see this here:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=204190...

But what about when using array based replication instead of vSphere replication?

Would it be the SRA that touches VMwtools on each VM, causing it to trigger a VSS quiesce? Or - is this not done?

If it is not done - how do we assure that the servers and applications are proplerly quiesced before they are replicated? Is there a way to do a "pre-replicate" power-cli or something, to ensure that (for example) SQL running on a VM is properly quiesced? We want full application consistency, not just crash consistency ...

2 Replies
basher
VMware Employee
VMware Employee
‎11-20-2015 10:14 AM

Hello

I would suggest talking to your array vendor. Some vendors offer for some of their models a in-guest agent that performs the integration between OS/App quiescing and the array taking the snapshot.

The SRAs themselves do not touch the guest.

Best regards

Stefan

Director - VMware Site Recovery Manager
vbrowncoat
Expert
Expert
‎11-20-2015 10:16 AM

With vSphere Replication VSS quiescing is an option. It is not on by default.

If you are using array-based replication you would need a solution from your array vendor to handle this. From what I've seen, these kind of solutions require the use of an RDM and an agent installed on the VM OS. I would suggest researching or contacting your particular array vendor to see what they offer. The SRA wouldn't be involved in this, it would just be the replication solution communicating with the agent, quiescing the application and then replicating the RDM.

I would also suggest investigating whether or not your application needs application quiescing. From what I've seen, most modern applications do fine without application consistency (if the VM where your application runs crashes or the host it is running on fails and the VM restarts hard, do you have problems with the application?)

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