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SLY
Asked: 2010-11-25 11:11:56 +0800 CST

What are some arguments against using virtualization in favor of multiple servers?

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I am settings up windows server 2008 environment.

I have 4 new servers with 12 GB RAM each.

I am looking to distribute the following roles:

1) Domain Controller / Active Directory

2) Exchange (E-mail)

3) File / Print

4) SQL Server

I am leaning towards installing each role on a different server. I think this would be easier for me to configure. Am I foolish to not use Hyper-V or VMWare? What types of factors should I consider when making this decision?

virtualization windows-server-2008 hypervisor

3 Answers

  1. Best Answer

    The real benefits of virtualisation are usually;

    • not having to buy extra servers - in your circumstance you've already bought new servers so this point is moot.
    • the ability to have zero-downtime hardware and base-OS updates through live-motion/vmotion - well this is great but requires shared storage - you may or may not have this in place.
    • the ability for a VM to restart on another host in the event of sudden hardware failure - again relies on shared storage
    • virtualisation usually impacts heavy disk use the most - in your case both Exchange and SQL server can be affected heavy by virtualisation more than many other applications if very busy - at least you know you're getting the full benefit of the hardware even if you missing out on the virtualisation benefits above.

    There are some other minor benefits of virtualising (driver stability, shared memory, fault-tolerance mode etc.) but these are the main ones.

    It depends on how busy you expect your Exchange and SQL boxes to be but you could have folded these four servers into one a single virtual server (you'd have needed more memory) or two servers if you's wanted the resilience features mentioned above (you'd have have to buy shared storage though).

    Personally I'd have virtualised the DC/AD box and file/print onto two boxes for resilience, possibly the Exchange too if it wasn't being hammered. I'd have left the SQL box physical with the possibility of a backup cluster member running in a VM - but that's me. It's a shame you're asking this question now, virtualisation is pretty much the norm these days.

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  2. 1) Most server virtualization platforms are not free. Does your budget account for that? 2) You need some sort of shared storage to To really take advantage of some of the features that virtualization offers. That again requires significant amount of money.

    The only real advantage that virtualizing on such a small scale offers is ability to use HW more efficiently.

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  3. As @Vitaliy said, a big advantage at your scale is "ability to use HW more efficiently." That DC machine is going to be seriously under-used, and so probably will be the file/print machine. Those two could both be VM hosts, and then you could have at least 3 guests - 1 file/print, and 2 DCs (one DC VM per host.). Without doing that, you only have one DC, so if it ever goes down, no one will be authenticating until it's fixed.

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