We are having an issue with several Windows 2012 R2 boxes running the HyperV role. The servers are all connected to their own APC SMART-UPS 1500 battery backups and have the USB data cables connected. Power management is being done via Windows power management.
The problem we're running into is that if the power goes out and Windows power management shuts down the server, the HyperV parent shuts down cleanly but the children all report dirty shutdowns. The "Windows was shut down unexpectedly" prompt comes up on all of the HyperV children when the parent is powered back up.
Interestingly, if the HyperV parents are rebooted or shut down manually from the console, the children have no negative effects--when the HyperV parent finishes booting, the children are all up and running normally where they left off when the parent was restarted or shut down.
I originally had the HyperV parent servers set to shut down when their UPSes got down to 60%. I figured maybe the estimated battery percentage was inaccurate, so today I set one of the servers (which doesn't have anything important on it) to shut down at 85%. After about 5 minutes, the server shut down. The UPS battery level indicated four out of five lights, so presumably at least 4/5ths of its power remained. However, after booting up the HyperV parent, the children all indicated that they had been subjected to a dirty shutdown.
Clearly the HyperV parent is smart enough to gracefully shut down the children under most circumstances, so why does it fail to do so when power management shuts down the parent?