Every virtual machine running on an ESX host consumes some memory overhead additional to the current usage of its configured memory. This extra space is needed by ESX for the internal VMkernel datastructures like virtual machine frame buffer and mapping table for memory translation (mapping physical virtual machine memory to machine memory). Two kinds of [...]

Recently we had a discussion about swapping, as Duncan mentioned in his article “Swapping” Swapped memory might not have impact on the performance of the virtual machine. There are scenarios when pages can be swapped out without experiencing performance problems. One common scenario is a bootstorm, i.e startup of many virtual machines at once. Bootstorms [...]

After publishing the article “impact of memory reservations” I received a lot of questions about setting memory reservation at resource pool level. It seems there are several common facts about resource pools and memory reservations that are often misunderstood. Because reservations are used by the VMkernel\DRS resource schedulers and (HA) admission control, the behavior of [...]