unable to create a 4 processor VM

[aktech]

Hello everybody, I have been trying to create a 4 processor Virtual Machine using esx 3.5 rev2, and at random points during the OS installation (dosent matter what OS I try to install) the install freezes and pegs out all 4 processors. I was wondering what may cause this and if there is anything I can do, aside from never creating a 4 processor VM. Attached are memory and CPU usage graphs for periods while the VM is locked up.

Thanks in advance.

[Troy_Clavell]

can I ask what would the need for a 4vCPU VM is? My advise would be to create the VM as a single vCPU first, you may find that the performance is quite nice.

[aktech]

originaly we were going to use the 4vCPU VM to run a large process, but mainly it was to test out the new software that we had bought, 2 vCPU VMs work fine, I was just wondering why an offered feature doesn't work.

[Troy_Clavell]

it's not that it doesn't work, it will work, but like you said, you will see degraded performance. Each vCPU is mapped to a phsycal CPU, so imagine it having to call all 4 physical CPU's before the VM can begin processing.

Don't just use something that is there, use what will work. In my opionion I don't see the need for anymore than 2 vCPU's and with that said 90 percent of our server VM's are running with a single vCPU

hope this helps a bit.

[khughes]

Like Troy said depending on your ESX hosts, you'll end up with a slower VM running 2 or 4 vCPU servers compared to ones with only 1 vCPU. This has to do with the scheduling of the processors to the VMs. A VM with only 1 vCPU only has to wait for a single core to become available to process the instruction set, where as a VM that has 2 or 4 vCPU's has to wait for 2 or 4 cores to become available at the same time for it to process the instruction set. As you can see if you only have 1 physical quad core processor, and you have a 4 vCPU VM, (even a 2 vCPU VM) it'll dramatically cut down your performance on that multi-vCPU box along with the rest of your VM's running on that host.

Like Troy, ~90% of our VM's are single vCPU boxes, and they run just as fast if not faster in some cases than when they were on physical duel CPU boxes.

• Kyle

[aktech]

thanks much for the help, luckily I don't have many processes that are that intense, and if I ever do come across any that just have to have that much CPU power, I will have to put them on a physical server that meets those specifications.

[Troy_Clavell]

you're welcome

don't forget, we love points. You can leave points for helpful/correct answers by utilizing the buttons on the left.

[khughes]

No worries, that is probably a safe bet if you have a server that is that big of a heavy hitter. Some physical servers just aren't candidates to run in a virtual environment.

• Kyle