Quad Core Processors

[VMGlugger]

If my server running ESXi has a Quad core processor - Is there any performance improvenent to be gained specifically choosing to assign 4 CPUs to a Server 2003 VM or if I just leave it at 1 core, will ESXi use all four cores to my best advantage ?

Does it make any difference ?

[Troy_Clavell · Accepted solution]

best practice is to always start with 1vCPU and work your way up. You will usually find 1vCPU will be sufficient. From there you would go to 2vCPU's. I don't think 4 is a good idea.

[satish_lx]

1 vCPU and 2vCPU depend on your system or OS kernel support for SMP or multi processor support so depend on that you should choise but recommanded is 1 vCPU and above that depend on your application and VM resource requirement.

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Thanks

Satish Patel

• Journey toward "Virtual world"

[TomHowarth]

Best Practice as Troy says is to use a single vCPU and grow to 2vCPUs, if you havea single Quad Core CPU a 4 way vCPU server is most definately not a good idea. VMware schedules resources by the number of vCPU. A pCPU or pCORE is required for each vCPU in the server to service instructions, this has been changed slightly in vSphere but in not in V

What this means in reality is that a single vCPU Guest will require 1 pCPU or Core per instruction cycle (in the guest) a dual vCPU guest will require 2 pCPU or Cores and a Quad vCPU guest will require 4.

the chances of a core or cores being available to service a guest is preportional to the number of cores in the machine, and the number of guest that host is running.

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Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author for the upcoming book "VMware Virtual Infrastructure Security: Securing ESX and the Virtual Environment”.