RE: Raid to Mirror comparison

        From:   Jeffrey M. Carey [SMTP:jeffreycarey@usa.net]
        Sent:   Tuesday, January 20, 1998 2:03 PM
        To:     MIDRANGE-L@midrange.com
        Subject:        Re: Raid to Mirror comparison

        In fact on a system before the "e"series, if you had RAID 5 you
had to
        mix protection - the load source could not be part of a RAID
set, so the
        best you could do is mirror.  

        One note on mirroring vs. RAID - when we've lost a drive on our
mirrored
        system, we haven't noticed (in fact, the performance gets better
since
        miroring gets suspended for that pair and available DASD
increases).  On
        RAID, the system will stop for a about five minutes when a disk
crashes.

        Available DASD doesn't increase - it just that the writes to the
mirrored drive don't happen.  In an environment with heavy write
activity this could translate to a slight performance improvement.
        On the other hand, with a lot of read activity this could be a
slight performance decrease, as normally when the read is issued to the
mirrored pair, one drive may respond slightly faster than the other.


... Neil Palmer                                     AS/400~~~~~      
... NxTrend Technology - Canada     ____________          ___  ~     
... Thornhill, Ontario,  Canada     |OOOOOOOOOO| ________  o|__||=   
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