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Server 2012 on VMware ESX - guest CPU 100% host CPU 30% how to allocate more Host CPU resources

Having troubles getting any decent performance out of MS Server 2012 on ESX 5.5

The Guest CPU flatlines at 100% sometimes whilst the Host CPU is only at 30%

Why doesn't the host allow more CPU resources to the guest

Host has 2 x quad core Xeons

We have tried 2 vCPUs. single core, and also 2 vCPU 4 core. We are currently running 4 x vCPU it is as good as it seems to be able to get. how can I get the ESX host to allow more CPU resources to be available to the Guest OS
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Avatar of Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
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We have not experimented with vCores as I had read that ESX does not differentiate between cores and sockets when it comes to allocating CPU resources, and that the Cores/sockets were only there to beat O/S CPU restrictions.

We originally had 4 x CPUS (sockets), and this did not seem to make any difference to the feel of the machine, or allow the guest CPU to really decrease to below 90-100% for the first 10-30 mins of booting.  though there appeared to be plenty of spare CPU resources that the host could have allocated.

I was under the assumption that the host CPU would be 100% available to the guest if it was the only VM on the box, I guess I don't really see any benefit in ESX throttling when spare resources are readily available.
I was under the assumption that the host CPU would be 100% available to the guest if it was the only VM on the box, I guess I don't really see any benefit in ESX throttling when spare resources are readily available.

This is not true, using a hypervisor is a compromise.

Cores and Sockets performance is often equal.

What is the sever function ?

What is the datastore ? e.g. SATA disks ?
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Thanks, adding additional CPU was helpful.
The server is a Microsoft exchange server and it seems to peak at close to 100% CPU for some time (up to 10 mins) after each reboot, before settling down to a usable level.

The effect of adding more sockets was noticeable after the initial CPU panic had settled down.
If its a 64-bit Exchange then its worth trying it with more RAM as well, but you may have done that already.