Please help - Cluster & SQL keep crashing

This happening more & more frequently - we have SQL installed on a cluster &
early in the a.m. the machine * SQL will reboot sporadically & sometimes han
g
- I am trying to narrow this down & determine if its SQL or the OS - I have
seen SQL start running out of memory(Error: 17803, Severity: 20, State: 14),
& then most recently we get "fcb::ZeroFile():   GetOverLappedResult(
) failed
with error 21." then "LogWriter: Operating system error 21(The device is not
ready.) encountered.".  I see 10-20 min before this logins are failing to
connect as well - the only thing I see strange SQL side is the previous DBA
had the server config'ed to do dynamic memory allocation & the max slider al
l
the way to the right full box mem, I know that is not recommeded - but other
than that, bad disk maybe in the cluster?  Could we just swap out the disk o
r
would we have to reformat the whole RAID?  Any info is greatly appreciated -
thanks.
--
John F.