I occasionally get this problem where my Debian system drops into rescue mode with the "Control-D to continue/enter root pw" prompt. This has happened before with no consequence, as I figured out all I need to do is a reboot, and it goes away.
The "start job" always lets the rest of the services start around the 20 sec mark, but this time it went the full 1min 30sec and then dropped into rescue mode. I have checked the disk with btrfsck, and nothing of consequence except for a dropped user space cache. Which shouldn't be a problem right?
The version of Btrfs is 3.17
Error message:
A start job is running for xxx.device
EDIT: Link to relevant parts of journalctl -xb: http://pastebin.com/E3XwnmCj The "parent" disk for the BTRFS volume is /dev/sdb1