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Are you looking at virtualizing SQL Servers?

I wrote an editorial for today on virtualization and some hints about how to plan a project. However I wonder if more people are actually thinking of implementing virtual servers. Drop a note in the comments below.

I have friends that have successfully virtualized SQL Servers in production, and I have some that have failed miserably. The key seems to be lots of testing and planning as well as carefully choosing candidates. Just as not every server instance is a good candidate for consolidation, not every instance is a good choice for virtualization.

Pick lightly loaded servers to start with and be sure you have enough resources.

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Steve Jones is the editor of SQLServerCentral.com and visits a wide variety of data related topics in his daily editorial. Steve has spent years working as a DBA and general purpose Windows administrator, primarily working with SQL Server since it was ported from Sybase in 1990. You can follow Steve on Twitter at twitter.com/way0utwest


Posted by hugh t on 28 July 2009

We are considering putting a production SQL 2005 Server and then possibly new development on SQL 2008 Server on our VMWare ESX 3.5 server. I have been reading every article I can get my hands on for insight and the experiences of others. Thanks for your editorial.


Posted by Steve Jones on 28 July 2009

You are welcome. We'd love to get more information about your experiences if you can write about it when you're done.

Posted by Wesley Brown on 28 July 2009

We have light duty SQL Servers on ESX 3.5, I personally won't put SQL Server on any VM that requires high IO and predictable performance, for some of the same reasons I won't put lots of named instances on a single server.

Even under the best of conditions the VM layer can add up to 30% IO overhead. Also, if you are running VMotion or VM cluster you have to use some kind of shared storage, that adds to the complexity as well. VMWare is pitching iSCSI shared storage solutions and at 1Gb/sec they don't meet many of my SQL Server requirements.

With that said, running a VM on SSD locally attached to the VM server may make a compelling configuration, so you loose 30% in IO on a physical disk that is a huge loss but if you are moving from a HDD solution to a VM/SSD solution the increase in IO and latency will more than offset that.

The other pitfall is over subscription of the host server. Since VMWare allows you to allocate more memory to the guest than exists on the host it is temping to over utilize the server in the name of consolidation.

I would also warn that now you have a VM admin, a server admin and a SAN admin in some cases just to make it that much harder to fix your SQL Server performance issues.

Just my thoughts on it.


Posted by Hugo Shebbeare on 28 July 2009

Thanks for the notes Steve, reading up now! And will update the MS Project SQL 2008 Migration Template I've been working on to reflect the VM project notes.


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