You can reconfigure the amount of memory allocated to a virtual machine to enhance performance.

Minimum memory size is 4MB for virtual machines that use BIOS firmware. Virtual machines that use EFI firmware require at least 96MB of RAM or they cannot power on.

Maximum memory size for a virtual machine depends on the host's physical memory and the virtual machine's compatibility setting.

If the virtual machine memory is greater than the host memory size, swapping occurs, which can have a severe effect on virtual machine performance. The maximum for best performance represents the threshold above which the host’s physical memory is insufficient to run the virtual machine at full speed. This value fluctuates as conditions on the host change, for example, as virtual machines are powered on or off.

The memory size must be a multiple of 4 MB.

Table 1. Maximum Virtual Machine Memory
Introduced in Host Version Virtual Machine Compatibility Maximum Memory Size
ESXi 6.7 Update 2 ESXi 6.7 Update 2 and later 6128 GB
ESXi 6.7 ESXi 6.7 and later 6128 GB
ESXi 6.5 ESXi 6.5 and later 6128 GB
ESXi 6.0 ESXi 6.0 and later 4080 GB
ESXi 5.5 ESXi 5.5 and later 1011 GB
ESXi 5.1 ESXi 5.1 and later 1011 GB
ESXi 5.0 ESXi 5.0 and later 1011 GB
ESX/ESXi 4.x ESX/ESXi 4.0 and later 255 GB
ESX/ESXi 3.x ESX/ESXi 3.5 and later 65532 MB

The ESXi host version indicates when support began for the increased memory size. For example, the memory size of a virtual machine with ESX/ESXi 3.5 and later compatibility running on ESXi 5.0 is restricted to 65,532 MB.

Prerequisites

Verify that you have the Virtual machine.Configuration.Change Memory privilege on the virtual machine.

Procedure

  1. Right-click a virtual machine in the inventory and select Edit Settings.
  2. On the Virtual Hardware tab, expand Memory and change the memory configuration.
    1. In the Memory text box, type the amount of RAM to assign to the virtual machine or select one of the suggested values from the drop-down menu.
    2. Select whether the memory is specified in MB or GB.
  3. Click OK.