DRS Advanced option "MaxHostMemOvercommitPct" for Maximum percentage of memory overcommitment allowed per host

Products

• VMware vCenter Server

Issue/Introduction

The MaxHostMemOvercommitPct advanced cluster setting allows administrators to define limits for memory overcommitment within a cluster.

Key Considerations:

• Setting this value to 0 completely disables memory overcommitment for all hosts within the cluster.
• It is important to note that this percentage is calculated based on the host's available resources (excluding kernel and user-reserved memory), rather than the total physical memory. This distinction must be factored in when designing your resource limits.
• You can verify the exact available memory for a specific ESXi host by executing the following command in an SSH session:

memstats -r group-stats -T -l2 -s gid:name:min:conResv:availResv:memSize -u mb 2> /dev/null | sed -n '/^-\+/,/.*\n/p'
---------------------------------------------------------------------------------
     gid   name                              min    conResv  availResv    memSize
---------------------------------------------------------------------------------
       0   host                           130563       9455     121108      13572
       1   system                           4391       4375     121124       4243
       2   vim                                 0       4872     121108        793
       3   iofilters                           0         40     121108         27
       4   user                                0        154     121108       8511
---------------------------------------------------------------------------------
conResv : consumed reservation
AvailResv : available reservation

From the result, 121108(host availResv) + 154(User conResv) value(in MB) is available memory.

Environment

vSphere 7.x
vSphere 8.x

Resolution

To set the DRS advanced option perform the following steps from the vSphere client:

1. Right-click the DRS cluster and click Settings > vSphere DRS > Edit > Advanced Options > Add
2. In the Option column enter: MaxHostMemOvercommitPct
3. Click in the Value column to enter the desired value in Pct, then click OK for this setting to take effect.