Equallogic SAN Replication

aix0 · 24 May 2011 at 12:06

Hi

I have a theoretical question that I'm hoping someone can help me out with.

I have 2 SANs, one designated as the primary which replicates to a secondary and run a virtualised instance of Exchange on an iSCSI attached ESXi host. The OS (VM) and the DB are stored on separate volumes. The VM is replicated every 1 hour and the Exchange DB is replicated every 15 minutes.

If I were in a situation where I had to failover to the secondary SAN, would I have any issues starting Exchange - as the VM could potentially be 1 hour old whereas the DB is only 15 minutes old? Would it matter that the OS and the DB are 'out of sync'?

Thanks

aix0 · 1 Jun 2011 at 07:25

Anyone?

Vanilla · 1 Jun 2011 at 08:44

It's quite common for OS volumes to be replicated differently to data volumes on the host, so not as far as i'm aware.

However, OS volumes rarely change so why not just replicate the OS volumes more often? Very little data will go accross (as long as you keep the page file on a local disk and not replicated).

On the Exchange subject directly - what version of Exchange are you running?

Microsoft and Exchange can be quite picky about Async replication, often going as far as to say 'don't call us, call you storage vendor'. If you raise a call and they get a sniff it might be down to the replication they'll just leave you hanging.

Skidilliplop · 1 Jun 2011 at 09:38

It should be ok as Equallogic SANs replicate a snapshot so as long as everything exchange related is snapshot at the same time you should be fine.
You can group volumes on Equallogic units though. So it might be safer for the "just in case" scenario to group the exchange IS volumes and the OS volume together so they're snapped and replicated in sync.