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I wanted to know if anyone has has any expirience of using SAN based snapshots and replication between SANs for disaster recovery. My main worries are around databases and applications like Exchange being recovered from a snapshot, has anyone tested this at all? I am looking at CDP products, but at looking at bare minimum requiresments based on snap shots.

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Yes, yes I have and it can work just fine but your success all comes down to what's doing the DB/file quiescing and is it talking to the SAN controllers to syncronise the two operations. We tend to use a combination of Oracle 10/11 and some of the HDS bolt-on tools but I'm happy to help you if you let me know what DB/OS/SAN etc. you have or are looking at.

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Hi, we are looking at EMC and IBM XIV, with OS's Windows, AIX, HP-UX, Applications, Citrix Oracle, MS SQL, Exchange. You've confirmed my theory that snapshots do not work by themselves, and additional software is required for each solution to provide a consistent recovery. – Nasa Feb 11 '10 at 13:51
All a snapshot does is let you backup a disk at a very specific point in time, that's fine if it's a file-level share like CIFS or SMB, if the file is open you just miss out on any mid-flight changes. The problem is with block-level shares/LUNS as the 'client' OS's manage them so they could be in ANY state - restoring back a disk in that state is highly likely to either confuse an unknowing OS, cause corruption or both. That's why we need the OS and/or apps like SQL servers to just take a moment to cut everything to disk so they're happy - then they shout "go" to the SAN which takes it's snap. – Chopper3 Feb 11 '10 at 14:45

Advanced Copy Services (aka Flash Copy Manager) also offloads the SAN snapshot it takes to Tape.
Is that good enough for your disaster recovery procedures ?

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