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Changes in support for virtual machine snapshots for SQL Server

First off, I have to say that writing a book and working on a challenging project for a customer at the same time does not translate well into having a lot of time to blog.  Shame on me – I need to do better.

Back to business.  Last year I wrote an article about using virtual machine snapshots with business critical applications like Exchange and SQL.  In it I provided a quote from Microsoft’s support policy for running SQL Server in a virtual machine.  The previous quote was the following (emphasis mine):

Virtualization Snapshots for Hyper-V or for any virtualization vendor are not supported to use with SQL Server in a virtual machine. It is possible that you may not encounter any problems when using snapshots and SQL Server, but Microsoft will not provide technical support to SQL Server customers for a virtual machine that was restored from a snapshot.

I recently looked at the same link again and was happy to see a revised version of this statement, found below:

SQL Server supports virtualization-aware backup solutions that use VSS (volume snapshots). For example, SQL Server supports Hyper-V backup.

Virtual machine snapshots that do not use VSS volume snapshots are not supported by SQL Server. Any snapshot technology that does a behind-the-scenes save of a VM’s point-in-time memory, disk, and device state without interacting with applications on the guest using VSS may leave SQL Server in an inconsistent state.

Though this was sort of implied with the previous support statement, it’s nice to see that as long as snapshots include a SQL Server aware VSS writer then the snapshot is supported.  This is great news for the virtual machine backup vendors like Veeam (and others) that have compatible VSS writers for SQL Server.  Many folks have been simply ignoring this restriction and using these products anyway so now it’s nice to know you have a support statement on your side if you need it.

I hope Microsoft decides to change their support statement for Exchange Server as well.  Right now it still reads the way it always has – no snapshots of any kind.  I’ll keep my eye on the Exchange virtualization support page and report back when/if that statement is clarified in the future.

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