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:


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


  • 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


  1. Fouad

    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



  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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