I've got a Server 2012 R2 physical box running as a Hyper-V 2012 R2 Host. Yesterday I logged into it and saw the prompt to enter the reason why the machine unexpectedly restarted.
Back on Server 08 R2 I could use dumpchk.exe or a bluescreen utility that would help isolate the reason for the unexpected restart. I don't see anything like that for Server 2012 R2.
Additionally, I checked the Startup and Recovery section located in System Properties. It shows the MEMORY.DMP file should be located at %SystemRoot%, which if you type into the run dialogue translates to C:\Windows\ on this server. I've enabled the view settings to show all the hidden files and OS files, etc. I don't see the MEMORY.DMP file located there. I've also searched the server for this file with zero results.
This server lives @ a data center with A+B power and all the redundancies we've learned to love. The hardware is less than 3 months old. The server has redundant power supplies. I'm not ruling out a power-failure but it seems unlikely.
I checked the Event Log and the only useful information there is one event that shows the date and time the machine rebooted without cleanly shutting down first.
Any thoughts on how to determine why my server rebooted unexpectedly? And yes I know the setting referenced above are default set to reboot the server upon a failure. I'm trying to ascertain what that failure is exactly.