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The sysadmins where I work are looking to re-organise our servers and they have suggested that we put the main production SQL DB on a virtualised server.

Is there anything they need to consider when doing this?

  1. Should we expect a drop in performance?
  2. If so how do we prevent it?

I know there are a lot of parameters here but some advice or experience would be useful.

Versions of SQL 2000 and 2005 (although we may upgrade the 2000 as part of the excercise)

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2 Answers

Do it, but do it right!

  1. There is a licencing impact. You will need to licence all the CPU's on the server, even if you dont use all of them in your guests (i.e. only one vCPU vm's) unless everyone accessing the SQL Server is covered with CAL's. We bit the bullet and got Datacentre and SQL CPU Enterprise licences for all the CPU's (and got multi-core servers)

  2. Performace impact? Yes, but slight. Usually you get all the goodness of upgraded backend SAN's, LAN and fibre connections. Also, you are better off avoiding the "one big vm to host all databases" and to split them into a couple of smaller vm's. As Brent says, there is a sweet spot of 2 vCPU's and 4GB RAM.

  3. Use 64bit OS and 64bit SQL 2005 / SQL 2008. I would stick to 32bit for SQL 2000 - personally I don't trust it!

  4. We use vmware ESX 3.5 over three nodes (HP DL380's, 32GB RAM, 2 CPU w/ 4 cores) to give us scalability and resilience (DRS / HA). Looking at vSphere 4 for host fail over for the most critical servers. Tip: Get as much RAM as you can in the hosts! We're starting to get a bit tight and you don't want to exceed the 60% mark on 3 hosts, or 75% on four hosts unless you want severe slow performance when you DO lose a host.

  5. We run over 20 SQL Servers (plus aother dozen related FE servers - web, SharePoint) on our cluster. We have another vmware cluster (4 node of DL580's) for other production (non-SQL) vm's. Over 170 vm's in total (90 are 'production')

  6. Even so. Even with a single host it makes it so much easier to manage, upgrade and gives you a much more future proof environment.

Good Luck - Guy

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I talked with Brent Ozar and others at the Quest Virtual Conference last week. He gave me a link to his site. I had asked pretty much the same question you are posing now.

Here and Here Good luck, we are testing out SQL on a Xen server w/ fibre Sans as I type.

Oh the sysadmins want to do it? There's an article for that.

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