Cant find much documentation regarding over committing of memory for VM's on a KVM host

Anees Patel asked:

Most operating systems do not use 100% of the available RAM all the time, having said that I am unable to find an approximation for this over provisioning. CPU cores is not a constraint for me,

I have a 64 GB KVM host, I would like to provision multiple 8GB machines, the machines remain under utilized for most of the time but always in running state, I would like to know the maximum acceptable number of VM’s that can be provisioned on this setup, without hitting any bottlenecks. The underlying storage is hard disk drives, with no SSD so there is little room for swap memory as it may impact performance

My answer:

I do not recommend any overprovisioning of RAM. I don’t think anybody does. If it’s overprovisioned even slightly, then something must swap and you then have the performance problem you are trying to avoid. Besides, RAM is cheap, but the problems you avoid by having enough are expensive.

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