ESXi

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  • 1.  vCPU vs cores per socket

    Posted Nov 09, 2012 04:50 PM

    I have a VMware ESXi 5.1 host with 2x Intel Xeon CPU E5-2640 (6 cores per CPU). vSphere shows me 24 cores (I assume because hyperthreading is turned on).

    I plan only 2 VMs for this host: 1 x SBS 2011 Standard and 1 x Windows  Server 2008 R2 Standard as Terminal Server. We have approximately 20  users which use this system.

    Should I assign 1 vCPU with 1 Core to each host or, because I have the up to 24, should I be more radical? I assume, the Terminal Server requires more CPU resources assigned.

    Any tips much appreciated.



  • 2.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 05:02 PM

    I would provide the VM with the necesary needed resources. Start with 1vCPU or maybe 2vCPU per guest and see how things work.



  • 3.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 05:10 PM

    Like troy said start with one.

    Its better to start with lower resources and scale up.

    when you over provision vcpus there is a lot of scedualing that needs to be done which in effect actually slows down your vm.



  • 4.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 05:11 PM

    Although I basically agree with Troy Clavell (starting low and increasing if required), I think with only two VM's planned for the host you could start with 2 vCPUs for the SBS Server and 4 vCPUs for the Terminalserver.

    André



  • 5.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 05:36 PM

    Thanks for your feedback.

    If I select 2 vCPUs for the SBS & 4 vCPUs for the WTS, how many cores per socket should I be selecting?



  • 6.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 05:39 PM

    using multiple cores on a VM is really only needed for applications that are licensed by the socket.  With that said, I would stick with 2vCPU 1 core and 4vCPU 1 core if this is hwo you are going to provision out the vCPUs



  • 7.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 06:00 PM

    Just for clarification... the vSphere Client Summary shows me 12 CPUs x 2,499 GHz. When I go to configure the hardware of the VMs, under CPU it shows me under virtual sockets: 24 and also under cores per socket: 24. Are you saying, select either 2 or 4 virtual sockets and just 1 core per socket. Then I am only using 6 of the available 24 - if I have the resource, should I not be allocating it?



  • 8.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 06:07 PM

    That's correct, you would use less cores than the host has in this case. You can certainly configure more vCPUs, however this may not result in more performance for the VMs. One of the benefits of virtual machines is to provide as many resources as required to multiple simultaneously running VMs.

    If you'd run a OS directly on the hardware, you'd have all 24 cores available, but I doubt you'd need them.

    André



  • 9.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 06:20 PM

    You are complicating things.  You add 2 socket.  That's 2 core.  You make them 2 core PER socket, now you have 4 core machine.  In virtual environment, a socket is by default 1 core.  You can replicate a VM to be identical to a physical server to test performance, but just start with the basics.

    Forget core.  Think of VM's as having sockets. Only change sockets, start with 1.  Then when you get more experience you can move on to more complex configurations such as cores per socket.  You can drive yourself insane trying to find a "perfect" VM.  In reality the biggest factor of *ANY* VM... is DISK, not CPU not Memory, DISK is *MOST* important.

    CPU will only be a factor *IF* your disks can outrun the pace that the CPU can read and manipulate data.  There isn't a disk on the planet (including SSD) that can keep up with CPU throughput.. a properly written program can keep CPU levels moderate and still make the disk scream...Even in a VM.

    Truth be told, programs are the real bottleneck.. not the technology or hardware.



  • 10.  RE: vCPU vs cores per socket

    Posted Nov 09, 2012 06:04 PM

    Contrary to popular belief TS is NOT CPU intensive.  TS will be fine with 1 vCPU. Memory and network are more important.