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We have 5 new Windows (2008 R2) servers on our disposal. We plan to configure them this way:

  • 3 web servers running IIS and DFS-replication (load balanced)
  • 2 SQL servers running SQL server 2008 R2 in Active/Passive clustered configuration

Now, for DFS-R and clustering we need two domain controllers and we don't have enough physical servers for them.

Can Hyper-V cluster be installed on the same hardware that is running SQL cluster?

What is better:

  • one node active for sql, other run virtual DCs
  • each node runs it's own DC?

Possible pitfalls? Things to be careful of?

Note: I don't want to virtualize SQL servers because of the high load. DCs should not be under any load at all. Web servers don't have enough RAM for virtualization and are not connented to shared storage.

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2 Answers 2

I know you say you don't want to virtualize the SQL servers but if the hardware you have is all there is, then I don't see you have much of a choice. I would not add the Hyper-V role to a SQL failover cluster (not sure if it's a supported configuration).

I'd create a Hyper-V cluster and then put a virtualized SQL cluster on it along with the virtual DCs. Better yet, and this is my personal preference, I'd find some older physical servers to run as DCs only because I still like my DCs to be single service physical machines.

Bottom line is I think you are somewhat stuck between a rock and a hard place. If you must virtualize the DCs, I'd create a clustered Hyper-v solution with virtual DCs (always keep them on separate physical hosts) and a virtual SQL failover cluster.

Something else to think about is backup. If you're going to use DPM it requires a separate physical server.

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If you don't have a physical DC, then you might encounter issues with lack of a DC while the hosts boot up. AD can co-exist with H-V, but clearly you'll need to watch for loading issues. –  Richard Jul 28 '11 at 7:17
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There is nothing wrong with virtualizing SQL server on Hyper-V, unless you have extreme performance requirements. And if you did, you'd never even think about running Hyper-V and SQL roles on the same server.. –  pauska Jul 28 '11 at 11:28

Something to note when virtualising domain controllers is that if Active Directory is not available (VMs turned off), you cannot bring the Hyper-V cluster online; and without the Hyper-V cluster online, you can't bring the domain controllers online... you MUST have a physical domain controller

If you can't purchase 2 additional servers to run AD then you'll have to virtualise the SQL cluster (both nodes)

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YES! I'm amazed that I forgot to put this in my answer. You must have AD online before the clustered hyper-v servers come up unless the hyper-v hosts are not domain joined, which you don't want to do; way too much pain regarding management of the hosts. Also remember to set start up delays on all servers so the switches can come up first, follow by the SAN (if you use one), then the DCs and finally the hyper-v cluster (one at a time), followed by other infrastructure servers as needed before the SQL and web servers come online. +1 to you. –  murisonc Jul 28 '11 at 23:35
    
Just a note that this is no longer true with 2012 –  Chance Feb 1 '13 at 0:22

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