Software based RAID5 has particularly poor write performance when the write
size is small, since the RAID5 has to do a read, adjust parity and a
writeback.  Unfortuantely small writes are what Netbackup mostly does in its 
index directories.

So, don't do it unless space and budget is your most pressing issue.
Mirror it.

> From veritas-bu-admin AT mailman.eng.auburn DOT edu  Fri Nov  2 09:46:55 2001
> 
> I'm setting up a file system for /usr/openv using volume manager with
> four disks, and I'm wondering if it would be better to make it a raid5
> system, or a concatenated mirror.  If I use mirroring, then my disk
> space is limited to that of the two disks, but with raid5, I get an
> extra disk space.  For performance reasons, what would be the best
> layout of disks?
> 
> thanks
> robert
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-- 
Mike Wei       Collective Technologies, a Pencom Company
Email: wei AT colltech DOT com