I want to write a PS script which will allow me to look at an ESX Cluster and determine, regardless of the Guest VMs state (on,off), how much remaining compute capacity I have. This is important b\c I can then look at this data and determine if I need to buy new hardware.
Clusters expose metrics called 'memory unreserved' & CPU unreserved. - “CPU & Memory currently unreserved and available to be reserved by virtual machines and resource pools. Look at this number when trying to determine whether you can create a child resource pool of a certain size, or whether you can power on a virtual machine with a certain reservation.” I found this info in the VMware DRS whitepaper.
Amount of unreserved memory
I'd like to know if anyone has any input on this approach. Am I overlooking anything? Has anyone seen a similar script out there already? Lastly, any direction of best to appraoch this would be greatly appreciated.
I must have missed your post.
Anyway, I don't think that these metrics are gathered for clusters.
The latest SDK Programming Guide (Revision: 20090113) states in Appendix A Performance Counter Reference that:
mem.unreserved for all rollup types is only collected for hosts and compute resources.
cpu.reservedCapacity in MHz (indirectly gives us what is unreserved) is only collected for hosts
Note also that a ComputeResource is not the same as a ClusterComputeResource.
The information you want is available in the ResourcePoolResourceUsage object.
Note the important remark on that SDK page about the difference between expandable and non-expandable resources !
The following script lists the unreserved Cpu and Memory resources.
$cluster = Get-Cluster <cluster-name> | Get-View $respool = Get-View $cluster.ResourcePool $unreservedCpu = $respool.Summary.Runtime.Cpu.UnreservedForPool $unreservedMem = $respool.Summary.Runtime.Memory.UnreservedForPool/1Mb Write-Host "Unreserved CPU (MHz)" $unreservedCpu Write-Host "Unreserved Mem (Mb) " $unreservedMem
If you run the script at regular intervals you should get a good view how the unreserved resources grow/shrink.
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