FYI,
we have a training setup where we run plenty of VCSAs for labs, and it happened the other day that the storage decided to go south.
Not bad, just in the midle of a course
When I was trying to restart everything, several of the VCSAs did complain about disks not having been cleanly unmounted, and forced me into single mode to do file system checks. That's where fun starts.
The root account now has the new VCSA shell tied to it, and it won't run in single user mode because some SO (shared object library aka DLL) was not available.
I had to trick grub into running /bin/sh to get access. Then LVM would not like the state of things, so ended up changing root's shell, rebooting into single user, fsck, then back to normal.
Not nice to discover in a real (i.e. production) DC.
-Carlos