Fixing "DRS Invocation Not Completed"

I ran into an error today that I haven't seen before. My vSphere 5.0 cluster displayed the message “DRS invocation not completed” on the Summary tab and, I noticed, it stopped moving VMs around automatically too.

I tried changing some of the DRS settings and running DRS from the DRS tab of the cluster just to try and see if that would get things going but to no avail.

Interestingly, I couldn't find any mention of the message on the VMware KB site or anything useful in Google. I was tempted to turn DRS off completely and then try re-enabling it but that would have removed my resource pools.

It was then that I noticed that some of the hosts weren't reporting any memory or CPU utilisation even though I knew them to be hosting VMs.

As an experiment I tried disconnecting and then reconnecting these hosts in turn. Once reconnected I started seeing DRS initiated vMotions occur to rebalance the cluster and the message disappeared from the cluster's summary tab.

So, I'm not sure why it happened but a simple, non-disruptive solution fixed it.

Just thought I'd share…