How does vSphere High Availability calculate the memory slot size of a virtual machine?

The vSphere HA slot size for memory is determined by the virtual machine's configured memory reservation combined with the estimated memory overhead needed by the ESXi host to run that virtual machine. To ensure any VM can be restarted, HA uses the values from the largest configured virtual machine in the cluster for this calculation.

Subtracting the overhead would result in an insufficient memory slot size, potentially preventing a VM from powering on during an HA event.

Using the overhead of the smallest virtual machine would underestimate the memory requirements for larger VMs, leading to a miscalculation of HA capacity.

Subtracting the overhead and using the smallest virtual machine's values would lead to a significantly inaccurate and insufficient memory slot size for HA planning.