Memory Compression

When a host’s memory becomes overcommitted, ESXi compresses virtual pages and stores them in memory. Because accessing compressed memory is faster than accessing memory that is swapped to disk, memory compression in ESXi allows you to overcommit memory without significantly hindering performance.

Pages that can be compressed to 2 KB or smaller are stored in the virtual machine’s compression cache, increasing the capacity of the host.
You can set the maximum size for the compression cache and disable memory compression using the Advanced Settings.

Procedure

1 In the vSphere Client, select the host in the inventory.
2 Click the Configuration tab.
3 Under Software, select Advanced Settings.
4 In the left pane, select Mem and locate Mem.MemZipEnable.

Memory compression is enable by default. No need to change this value. Just below this value shown below select Mem and locate Mem.MemZipMaxPct. The value of this attribute determines the maximum size of the compression cache for the virtual machine.
5 Enter the maximum size for the compression cache. By default it is configured as 50

This value is in percentage corresponding to configured memory size of virtual machine. This is maximum size Host can use to compress memory pages of VM.

6 Click OK.

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