ESXi

Guys,

my question may sound trivial but i need to have it clear.
If i allocate certain amount of RAM and CPU (without reservation) on some VMs, if the VMs are not fully using the amount allocated, is it used by other VMs.
I'm asking it as more and more i have VCOPs reports with many oversized VMs and i besides i know i have to take actions to reduce the overhead of each VM , i need to know if memory and CPU are shared dynamically in case of needs from other VMs.

Many  thanks in advance.

Daniele

Short answer yes, if no reservation are set, resources are allocated dynamically.  In the event of contention, shares values will be used for resources allocation.  VMs with lots of unused memory are taxed (idle tax) and reclaimed through ballooning.  The important thing is to know what workload the vm is running, and if VMs are using memory to cache content, i.e sql or exchange and these could get reported as oversized VMs.  Monitor the VM over period during normal business cycle and size your vms accordingly.