When planning performing rightsizing events on a customer’s estate I am usually requested to estimate the number of new VMs which could be placed into estate on the resources freed up by rightsizing.
This can be calculated relatively easily by hand, but who wants to do that when you can have something else do it for you, and even utilise it on a dashboard as a KPI
My customer in this example have a guideline they use for an average machine on their estate which is 4 vCPU and 32GB RAM.
So in the first example I will show the code with a fixed VM size.
This calculation uses the floor function to take the lowest of an array of numbers. More details here:
Estimate remaining VM Overhead using vROps – Advanced Super Metrics
The calculations it’s using here are the number of excess vCPU metric, divided by 4 vCPU for our guideline VM, and the amount of excess memory metric, convert from KB to GB and divided by 32GB RAM
Remember the depth setting allowing this supermetric to run at a higher grouping level such as vCenter or Custom Group
floor(min([((sum(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=summary|oversized|vcpus, depth=5}))/4),(((sum(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=summary|oversized|memory, depth=5}))/1048576)/32)]))Now this can be further expanded by instead of using a fixed VM size, we could take the average VM size of the grouping we are running this supermetric against.
To do this we would replace the “4” and “32” with a calculation for average size
For vCPU this would be
avg(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=config|hardware|num_Cpu, depth=5})
for RAM this would be
avg((${adaptertype=VMWARE, objecttype=VirtualMachine, metric=config|hardware|memoryKB, depth=5})/1048576)
so our full calculation for estimating how many of the average VM size could be reclaimed by rightsizing would be:
floor(min([((sum(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=summary|oversized|vcpus, depth=5}))/avg(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=config|hardware|num_Cpu, depth=5})),(((sum(${adaptertype=VMWARE, objecttype=VirtualMachine, metric=summary|oversized|memory, depth=5}))/1048576)/avg((${adaptertype=VMWARE, objecttype=VirtualMachine, metric=config|hardware|memoryKB, depth=5})/1048576)
)]))