The vSphere Client shows information about host memory allocation.

The host memory fields are described in Host Memory Information.

Host Memory Information

Field

Description

Total

Total physical memory for this host.

System

Memory used by the ESX/ESXi system.

ESX/ESXi uses at least 50MB of system memory for the VMkernel, and additional memory for device drivers. This memory is allocated when the ESX/ESXi is loaded and is not configurable.

The actual required memory for the virtualization layer depends on the number and type of PCI (peripheral component interconnect) devices on a host. Some drivers need 40MB, which almost doubles base system memory.

The ESX/ESXi host also attempts to keep some memory free at all times to handle dynamic allocation requests efficiently. ESX/ESXi sets this level at approximately six percent of the memory available for running virtual machines.

An ESXi host uses additional system memory for management agents that run in the service console of an ESX host.

Virtual Machines

Memory used by virtual machines running on the selected host.

Most of the host’s memory is used for running virtual machines. An ESX/ESXi host manages the allocation of this memory to virtual machines based on administrative parameters and system load.

The amount of physical memory the virtual machines can use is always less than what is in the physical host because the virtualization layer takes up some resources. For example, a host with a dual 3.2GHz CPU and 2GB of memory might make 6GHz of CPU power and 1.5GB of memory available for use by virtual machines.

Service Console

Memory reserved for the service console.

Click Properties to change how much memory is available for the service console. This field appears only in ESX. ESXi does not provide a service console.