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lindelof
Asked: 2010-10-21 06:54:10 +0800 CST

How should I size a server that will run several virtual machines?

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possible duplicate: Assessment & Planning Toolkit

I'm planning to rent a dedicated server from our provider that will host several services (SVN, LDAP, etc) each as a dedicated virtual machine. I guesstimate there will be between 5-10 servers, none of which should be under a particularly heavy load.

If I run this under Xen, how much memory/processing/disk should I ask for? Roughly? Any rules of thumb?

virtualization xen sizing

3 Answers

    1. Figure out how much min/average/max CPU each VM will need, add them together, add 1-1.5Ghz for the OS and hypervisor
    2. Add all the VM's memory requirements together, add ~15-20% plus the OS.
    3. Add all the VM's disk requirements together, add 10% plus whatever the OS plus swapfile needs.

    Can's say any more without knowing a lot more indeed.

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  2. Depends on the OS, but for a network that small doing basic services, I'd probably setup the VMs with access to 1-2 processor cores and 2 GB of RAM each. Of course, if you're talking about hosting some types of systems (Microsoft Small Business Server, for example, then you need a MINIMUM of 4 GB for that VM and frankly, even for a small environment like that, I'd go with 8 GB for it.

    But that's a really basic suggestion based on the really limited information you've provided.

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  3. Are you wedded to Xen? If not, consider using OpenVZ. Its resource requirements are much lower than Xen. In my experience, one can fit 2 to 4 times as many OpenVz guests as Xen guests on a given hardware platform. The main drawback is that all OpenVZ guests share the same kernel (although each guest is still otherwise independent and can be stopped, started, and rebooted independently of the others), and thus somewhat less isolated from each other than Xen guests.

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