Before you manage memory resources, you should understand how they are being virtualized and used by ESX/ESXi.

The VMkernel manages all machine memory. (An exception to this is the memory that is allocated to the service console in ESX.) The VMkernel dedicates part of this managed machine memory for its own use. The rest is available for use by virtual machines. Virtual machines use machine memory for two purposes: each virtual machine requires its own memory and the VMM requires some memory and a dynamic overhead memory for its code and data.

The virtual memory space is divided into blocks, typically 4KB, called pages. The physical memory is also divided into blocks, also typically 4KB. When physical memory is full, the data for virtual pages that are not present in physical memory are stored on disk. ESX/ESXi also provides support for large pages (2 MB). See Advanced Memory Attributes.