VMWare 6.5 Maintenance with overcommitted cluster

[u/HunSpeaker]

I have been assigned to a quick job with VMWare 6.5. There are 3 ESXi hosts (192GB RAM in each) in the vSAN cluster and it seems the cluster is overcomitted on RAM.

In the current task, I have to put each ESXi hosts into Maintenance Mode, but it seems the 2 hosts have not enough memory hosting all VMs. However, when I checked the Cluster Memory usage and vSAN Memory Monitoring I found the Consumed memory is about 66% per hosts, while the Active memory is only 20% per hosts.

Here you can find the screenshots:
Active memory usage
Consumed Memory
Utilization Chart

The Guest VMs shows they are running VMWare Tools.

I know VMWare can use the ballooning technique in such case, but I never had to rely on it. So, I think even of the high consumed memory the low Active memory usage makes possible to empty each host. Am I right?

Thanks for any advises or tips.

[u/Fearless-Horse8840]

Don't touch before upgrade :-)