I have a VMWare ESXI 5.0.0 (it's a bit old, I know) host with three guest VMs on it. For reasons unknown, the guests will not use much of the availble CPU resources.

I have all three guests in a single pool, with the hosts all configured to use the same amount of resource shares, so they're basically 33% each. The three guests are basically identically configured as far as their VM resources go.

So the problem is, even when the guests are performing what should be very 'busy' activitites, such as at bootup, the actual host CPU consumed is something tiny, like 33mhz, when seen via vSphere console's "Virtual Machines" tab when viewing properties for the pool. And of course, the performance of the guest VMs is terrible.

The host has plenty of CPU to spare. I've tried tinkering with individual guest VM resource settings; cranking up the reservation, etc. No matter. The guests just refuse to make use of the abundant CPU available to them, and insist on using a sliver of the available resources.

Any suggestions?

Update after reading various comments below Per the suggestions below, I did remove the guests from the application pool; this didn't make any difference. I do understand that the guests are not going to consume resources they do not need. I have tried to do a remote perfmon on the guest which is experiencing long boot times, but I cannot connect to the guest remotely with perfmon (guest is w2k8r2 server). Host graphs for CPU, Mem, Disk are basically flatlining; very little demand. Same is true for the guest stats; while the guest itself seems to be crawling, the guest resource graphing shows very little activity across CPU, Mem, Disk.

Host is a Dell PowerEdge 2900, has 2 physical CPU,20gb RAM. (it's a test/dev environment using surplus gear) Guest1 has: VM ver. 7, 2vCPU, 4gb RAM, 140gb storage which lives on a RAID-5 array on the host. Guest2 has: VM ver. 7, 2vCPU, 4gb RAM, 140gb storage which lives on a RAID-5 array on the host. Guest3 has: VM ver. 7, 1vCPU, 2gb RAM, 2tb storage which lives on a RAID-5 ISCSI NAS box

Perhaps I am making a false assumption that if a guest has a demand for CPU (e.g. Windows Task Manager shows 100% CPU), the host would supply the guest with more CPU (mem, disk) on demand. Another Update After checking the stats, it would appear that the host is indeed not busy at all, neither is the guest. I believe I have a good idea on the issue, though; a messed-up VMWare Tools install. The guest has VMware Tools on it, but the host says it does not. VMWare Tools refuses to uninstall, refuses to be upgraded, refuses to be recognized. While I cannot say with authority, this would appear to be something worth investigation. I do not know the origin of the guest itself, nor the specifics on the original VMWare Tools install. Following various bits of googling, I did come up with a few suggestions that went nowhere. To that end, I was going to delete this question, but was prompted not to do so since so many folks answered.

My suspicion right now is; the problem truly is the guest; the guest is not making a demand on the host, and as a natural result, the host is treating the guest accordingly.

My Final Update I am 99% certain the guest VM had something fundamentally wrong with it re VMWare Tools. I created a clone of a different VM with a near-identical OS config, but a properly working install of VMWare tools. The guest runs just great, and takes up it's allotment of resources when it needs to; e.g. it eats up about 850mhz CPU during startup, then ticks down to idle once the guest OS is stable.