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I've just received an upgraded Host machine, and am looking to push some of those advances to my workstations Guest OS(s). In particular, I used to have a single processor, with 2 cores, so my Guest OS only had 1/1.

Now, I've got a single processor with 8 cores, so I'm curious about what would be recommended for my Guest OS now?

  • 1 processor/4 cores?
  • 2 processors/2 cores?
  • 4 processors/1 core?

My instinct says to stick with the number of physical processors (or less), but, is that based on reality? I spent a good while looking for an answer to this, but perhaps my google-karma isn't in my favor today.

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Is your guest using up the processing capabilities it has as it is now? – OldWolf Sep 8 '11 at 20:54

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I don't know if this information is still valid, but in the not-too-long-ago past, additional guest CPUs didn't scale nearly as well as host CPUs did. In fact, best recommendation was to stay with single CPUs in your guest configurations unless you were specifically testing/debugging multithreaded software in your guests and required an SMP environment.

Edit: This answer is particular to desktop virtualization, not server virtualization.

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so, you're saying 1 processor, with a single core? – reidLinden Feb 14 '11 at 16:26
Yes. Does VMware workstation allow for setting those values independently now? I haven't used it since ver 6, and it was just a # of CPUs. If you're going to do multi-core/multi-CPUs in your guests, I doubt it much matters which way you scale things unless licensing considerations (# of "sockets" vs. # of "cores") come into play. e.g. XP Home only allows 1 socket, but up to 4 cores, while XP Pro allows for 2 sockets. – afrazier Feb 14 '11 at 16:50
yea, I appear to have the option to pick "# processors" and "# cores" independently... My Host machine has 1 processor with 8 cores, on a windows7 Professional, and my (main) guestOS is a windows server 2003... – reidLinden Feb 14 '11 at 17:07
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At most I give my guest OS 2 cores. It doesn't matter if you do 1 processor 2 cores or 2 processor 1 core each. The procesor setting is for compatibility reasons. Processor/cores don't scale so well for guest OS because of core/processor process scheduling. 2 cores seems to be the sweet spot.

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