I forget who originally posted the message asking about mirrored discs,
but I figured I'd put my $.02 in.
 
At our shop (980-100 running 4.0 MPE/iX) we use mirrorring extensively.
 We have four volume sets (including system) and all three user sets
are mirrored.  Our shop runs 24 hours a day 7 days a week, so we need
maximum system availability.  Mirrorring elimates the problems of
downtime do to a disc problem (here this consists mainly of power
supplies burning out).
 
A disc fails and our operators acknowledge it on the console, place a
service call to HP and they hot swap it or install a new power supply.
Then it is a matter of resyncing the drives and done.  No down time and
the users don't even know there was a problem.
 
Gary Paveza
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My opinions are my own and do not reflect that of my employer..etc
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