So sometime along yellow brick firmware road HP changed (and maybe your
vendor did too) the output of what happens when the write cache is off due
to failed batteries attached to the card/cache. (and no they don't always
beep with a self test in case someone happens to be walking near your cage,
and yes you will be wondering why batteries attached to these things are not
hot swappable.)
So yeah -- even if you were pretty sure some code had properly checked with
say nagios checks (or whatever) and were monitoring them... if someone
hasn't replaced a dead battery in a while you should probably be wondering
why.
Now go forth and test/ your HA/DR plans, check you raid and UPS batteries,
test your monitoring (again).
-M