Use case – right-sizing large VMs
The target user for this use case is the VM owner.
This is the most popular request from my clients. It is common for VMs to be sized conservatively by the application team. The result is that many VMs have too many vCPUs and vRAM. A larger VM does not necessarily mean a better-performing one. Once VMs are in production, it can be difficult to right-size them as it requires downtime and testing.
Besides wasting company resources, there are several disadvantages of having an oversized VM:
It takes longer to boot. If a VM does not have a reservation, vSphere will create a swap file the size of the configured RAM.
It takes longer to vMotion.
The RAM or CPU may be spread over a single socket. Due to the NUMA architecture, the performance will be inferior.
It will experience higher CPU co-stop and CPU ready time. Even if not all vCPUs are used by the application, the Guest OS will still demand all the vCPUs be provided by the hypervisor.
It takes longer to snapshot...
