vSphere 6 ESXi memory states and reclamation techniques

vSphere 6 uses the well known memory reclamation techniques you may already know from previous versions:

  • transparent page sharing (TPS)
  • memory ballooning
  • memory compression
  • memory swapping

The memory reclamation technique that is used depends on the ESXi host memory state, which is determined by the amount of free memory of the ESXi host at a given time.

With vSphere 6 VMware introduced a new memory state, called “clear state“.

So vSphere 6 knows five different memory states associated with one or more memory reclamation techniques to reclaim memory:

esxi-memory-reclamation-vsphere-6

But which treshold of free memory is associated with which memory state?

ESXi uses a value called “minFree” for the memory state calculation. minFree is a dynamic value and depends on the ESXi host memory configuration.

You can calculate minFree very easy for your ESXi host:
for the first 28 GB of physical RAM in the ESXi Host: minFree = 899 MB
+ add 1 percent of the remaining RAM to your calculation

minFree calculation vsphere 6

Figure: „minFree calculation example vSphere 6:

In the example above the ESXi host has 100 GB memory:
for the first 28 GB RAM minFree = 899 MB, for the remaining 72 GB (100 GB – 28 GB) we have to add 1% to minFree: 1% of 720 GB = 720 MB -> minFree is 899 MB + 720 MB = 1619

Thresholds:

  • high state: enough free memory available
  • clear state: <100% of minFree
  • soft state: <64% of minFree
  • hard state: <32% of minFree
  • low state: <16% of minFree

If you want to know the memory state of one of your ESXi hosts you can use ESXTOP (extract from the vSphere 6 ESXTOP quick Overview for Troubleshooting” diagram):

memory state esxtop vsphere 6

Open ESXTOP and type “m” for the memory tab. The host memory state is displayed in the first line on the right.

You want to learn more about ESXTOP?

Take a look at the vSphere 6 ESXTOP quick Overview for Troubleshooting” diagram:

ESXTOP vSphere 6

2 Comments

  1. Fouad

    Hi,
    After some test,

    I think Hight state is when free RAM higher than 400% minFree

    And Clear between 400% & 100% min free.

    My article about it in French gut you can use Translator

    http://vroomblog.com/vmware-state-memoire-de-lesxi-high-clear-soft-hard-low/

    Cheers

  2. Raj Navalgund

    Hi Andreas,

    This definetely helped me to understand the states of host memory state,Thank you.

    Raj Navalgund

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