While setting up my home lab, I did not bother/think to check if the NAS was going to hibernate itself or its disks after a period of inactivity. Sure enough after I built my cluster + SCVMM + what not, the hosts would drop their disks – PDL. Fix?
The disks were meant to hibernate after 20 mins of activity by default. I went into the Control Panel > Hardware & Power > HDD Hibernation and un-checked “Enable advanced HDD hibernation to minimize power consumption for DS412+:
All’s been well since. Full steam ahead!