Windows VM in background -- one Xeon enough?

Discussion in 'Mac Pro' started by mlts22, Feb 15, 2011.

  1. mlts22 macrumors 6502a

    Oct 28, 2008
    For a Mac Pro that most likely will be running a Windows VM in the background constantly using VMWare Fusion, would a quad-core machine suffice for this (dedicating 1-2 cores to the VM), or would it be better to go for an 8 core?

    The machine will be doing some Logic Audio, Aperture, and also Objective-C build work here and there.

    I'm not sure how much a drag it would be on the CPU, so wondering if the quad core Xeon would be enough for a VM for general Windows workstation use.
  2. brentsg macrumors 68040

    Oct 15, 2008
    Obviously it depends on what you're doing with the VM, but if you have plenty of RAM it should be fine.

    I'm using a 6 core MP with 12GB RAM, and I will often have 3 windows VMs in use and get only minimal page-outs. About to pop in another 4GB RAM and I should be good for a couple additional VMs.

    I put my OS and OSX apps on an SSD, and the VMs on a 10,000 RPM drive and I think it helps tremendously.

    As long as you understand that you're robbing resources from your OSX apps and plan accordingly it should be fine.
  3. mlts22 thread starter macrumors 6502a

    Oct 28, 2008
    So, about 18-24 GB of RAM then, as opposed to another CPU? That makes sense, because VMs tend to be more I/O intensive than actually nailing the processor.
  4. cutterman macrumors regular

    Apr 27, 2010
    Those apps you will be using in the VM can consume lots of CPU cycles. If you are running the VM and doing anything meaningful in OS X at the same time you will be happier with 8 cores.

    +1 on previous post: Buy plenty of RAM and put your VM on a 10k raptor HD (I use 2 of them in Raid 0)
  5. brentsg macrumors 68040

    Oct 15, 2008
    Look at it like this. You're essentially dedicating a certain # of cores to the VM. Just assume them as gone from your OSX machine and consider whether that leaves you enough CPU for your OSX tasks.
  6. dyn macrumors 68030

    Aug 8, 2009
    You can not dedicate a core to any OSX virtualisation application whatsoever. What you can do is set it up to use virtual cpu's (vcpu) so it looks as if the virtual machine has 2 or even more cpu's. This is useful if you want to test multicore/cpu stuff or use things that can benefit from it. It does not dedicate it to a physical core/cpu! If you want to us vcpu's be careful to how many you use. If your machine has 8 cores you can use 4 vcpu at a max, if it has 4 cores this will be 2, if you only have 2 you can not use more vcpu's (just 1). If you disregard this you will cause performance problems.

    Hardly anything. Memory and I/O are the main parts for virtualisation. Using lots of memory and a ssd will make much more difference than using a faster cpu or more cores/cpu's. I'm using the cheapest Mac Pro with 12GB of ram, a ssd (OCZ Vertex) and the standard 1 TB WD Caviar Black that came with it. Running vm's on the ssd and the hdd gives me great performance. I'm currently running a vm with ESXi (with 3 vm's: FreeBSD, Ubuntu and DOS) as well as a 32 bit Win 7 vm (configured with 2 vcpu's and 3 GB of mem). It works great when working in the vm's and I'm not even noticing VMware Fusion is running in the background. Looking at the cpu usage reveals the Win7 is doing 2.5% (it is currently idle) and the ESXi vm is doing 106.7%. I'm not doing much other stuff so in grand total the Mac Pro is currently doing nothing, it's "sleeping".
    This behaviour I've noticed on my MacBook in 2006, on the MacBook Pro in 2008 and on my current MacBook Pro from 2010. Switching from hdd to ssd made a very big difference as well as going from 2 to 4GB or 4 to 8GB.

    In other words: if you want to do virtualisation worry about memory and hdd, not about cpu. However, if you want to test/use multicore/cpu in a vm (because it would benefit from it) then worry about the amount of cpu's/cores as well (but not about its speed).
  7. minifridge1138 macrumors 6502a

    Jun 26, 2010
    You'll be fine with even the base mac pro.

    If you have spare money, buy ram.

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