We had a server that was in production for well over a year. On
Tuesday, late in the day, a user reported that the drives could not be
accessed. Upon looking at My Computer on a Win7 machine, all drives on
that server were disconnected. We went into the ESXi 5.5 console for
the respective server and noticed that it was at the initial startup
screen getting read to select the default option from the SLES menu to
start the server.

We do not know why it appears to have spontaneously rebooted. We did
expand the ESXi virtual disk about 3 hours earlier for one of the drives
and expanded the pool without incident.

We looked at the warning log and and could not see anything that might
indicate the cause of the restart. The warning log had normal log
entries until the point of restart and then continued with the new
startup information several minutes later.

It there anywhere else we can look to determine what may have caused the
system to just restart. We don't think someone in the IT department
just powered off the virtual machine. We also just had our consultant
recently upgrade us from ESXi 5.1 to 5.5. I don't know if there are any
logs there that might help indicate the cause of the problem.

Is there anything we can do to track more information for future
incidents if they occur.