I thought I was doing the right thing by powering off all VMs before performing an update on my NAS, but I guess not. My Synology NAS gets updates quite frequently and in an effort to keep it up to date, I don't like to delay installing them. After the update, all the machines were grayed out and I was forced to reboot the host. I've seen others have to remove the machines from inventory, run a command line tool through ssh, re-add them to inventory, etc. As fun as that sounds, all of this seems unnecessary because of a simple datastore reboot. Is there a fix or workaround for this? I certainly don't want to be rebooting my host every time I install a NAS update.
Because your nas is a single storage processor model I think you should reboot all your infrastructure.. Another way, depending on your license, is to storage vmotion your vms to another datastore if available; but in all ways, before doing a storage update, try to remove datastore using vsphere client, after vm evacuation is done.