Great post – I find so many VM’s over subscribed for no good reason.


I thought this example may be useful to show the benefits of Right sizing a virtual machine.

The VM is an SQL Database server with 4 vCPUs on a cluster which is highly overcommitted with lots of oversized VMs.

As we can see by the below graph, the CPU ready was more or less averaging 10% and on the 24th of July most vCPUs spiked to greater than 30% CPU ready each. ie: 30% of the time the server is waiting to be scheduled onto the pCPU cores.

The performance of applications using databases hosted on the server were suffering serious issues during this time.

On the  24th the VM was dropped from 4 vCPUs, down to 2 vCPUs and the results are obvious.

CPU ready dropped immediately (even in a heavily over-committed environment) to around 1% and CPU utilization remained at around the same levels. Performance also improved for…

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