Re: [Xen-users] Hardware requirements for Xen

[John Sherwood <jrs@xxxxxx>]

You don't need a "powerful" server to run Xen by any means, but to run Xen and 30 VMs is a different story.  Not to be pedantic, but the requirements for power come entirely from your workload, not from the (extremely lightweight) Xen hypervisor itself.

Bare minimum you'll want 1 core + 512 MB RAM for each VM, then a core and additional RAM for the dom0.  With 30 VMs you're going to want a pretty beefy amount of RAM for your dom0, and you'll probably need another core as well.  You'd probably want at least 2 NICs so that you have more bandwidth when you've got a couple dozen VNC connections active.

However: I have no experience running that many HVM machines at once - I've run 16 VMs on an 8 core, 16 thread host before, but that was with PV.  At any rate, I suppose my suggestion for your server would be:

• 32 cores (using either something like opteron 62XX interlagos, or Xeon E5-26XX)
• 32+ GB RAM
• 3+ NICs, 1 dedicated for management of dom0

If you have any boxes lying around, I might also suggest trying to load an 8 core server with 7 winXP VMs and seeing how it performs with all the VMs having VNC active - that should give you a decent feel for whether you need to scale up your requirements before purchasing or allocating more expensive hardware.  Keep in mind that you want to scale up the dom0 memory as you add more VMs though, and the load on the dom0 will increase with more VMs as well - due to the HVMs, the dom0 load will increase with the number of virtualized peripherals.

On Mon, Jun 4, 2012 at 4:10 PM, <baileyp@xxxxxxxxxxxxxxxxxx> wrote:

   I need to figure out how powerful a server I need to run Xen. Specifically, I'm looking to replace about 30 Windows XP desktops with low-power thin-clients using VNC to connect to virtual desktops provided by Xen. This is supposed to be a cheap interim step while we work to replace an Access system that most of our employees use with a web-based program, at which point most of the VM's would be deprecated (as the thin-client PC's would simply be used to connect to the intranet site).

   So, in short -- I'm looking to replace about 30 WinXP desktops with VM's hosted by Xen, and I need to figure out how much memory and CPU power I'll need to make this feasible. Is there some guideline I can use to figure this out?

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