I have a case open with support on this but I wanted to see if anyone else has run into it. We upgraded from ESXi 5.0/5.1 with vCenter 5.1 to ESXi 6 and vCenter 6. After the upgrade, DRS has started throwing this error on our hosts:
"Unable to apply DRS resource settings on host. The available Memory resources in the parent resource pool are insufficient for the operation...."
It'll appear usually after a vMotion (on or off) or a reset of a vm. I did manage to clear it by reducing memory reservations on VM's but that's only a temporary fix. Otherwise it appears to just randomly clear itself.
Looking at a vm's memory resource allocation shows it cannot reserve any memory (the orange triangle is at the far left.)
Across the cluster I have 2TB of memory, allocated to VM's I have 475GB. Looking at the vm's on a host when this alarm is active also shows plenty of memory available.
Support has tried disabling and re-enabling HA. That cleared it for about a day before it came back. We've tried removing the pools.xml file, restarting the hosts and vCenter.
VM's and Hosts are the same as they were under ESXi 5.0/5.1 and vCenter 5.1. This error never appeared on that version.
Thank you in advance for any insight.