We RARELY have a problem with our mirrored drives.
We're using Jamaica arrays on our private volumes,
and a Nike array on our System volume.  And of course
we made sure we're using a powerful enough processor
and RAM to handle the overhead.  (Read 979KS two
processors, 1GB RAM, 55 disc drives 38 of which are
mirror/pairs.  Performance is excellent.)

When one of our mirrored drives DO go down, it is a
simple matter of calling HP to come in and swap the
drive and re-synch it.  Granted for the period of the
downed drive, we're at risk for the time it's mirror
is down.

We've had 3 instances of downed mirrors in 1998.
Swapped online, not a problem.

Our conscientious HP hardware support also took the
time to check the firmware one these drives, as
well as their controllers.  Older firmware was found.
He made sure they were updated (read "swapped") during
"scheduled" down time.  This was sure to avoid any
potential future problems.

Tracy M. Johnson
TRW Automotive Electronics

> -----Original Message-----
> From: Rick Ingham [mailto:[log in to unmask]]
> Sent: Wednesday, January 19, 2000 10:52 PM
> To: [log in to unmask]
> Subject: Re: Mirror/iX
>
>
> Some observations based on my company's experience:
>
> 1) The software mirroring adds a 25% CPU load to all the
> process activity as
> additional overhead.
>
> 2) As often as it saves us, it also kills us.  Half the time
> the wrong drive
> of a mirrored pair goes off-line.  If the on-line drive is
> the one with
> errors, we have to reload the system, since it can't be
> re-sync'd nor can
> the other drive simply be switched on as the good one.
>
> 3) System reloads with morroring turned on significantly increases the
> reload/down time.
>
> 4) Reloading the system, then starting the resync, and
> letting users back on
> the system while the drives are resync'ing can cause another failure
> requiring again another reload.
>
> Bottom line:
> a) since the number of drives has doubled, the failure rate has also
> doubled.
> b) Doubling the failure rate and having Morroring fail to
> keep the system
> running properly half the time, means a net wash on reliablity.
> c) we have spent gobs of money on the extra drives, cabinets,
> SCSI cards.
>
> Net, we have paid HP an aweful lot for absoluty no benifit
> and a lot of
> headache.
>
> I'm trying to convince the powers that be to simply turn off
> the mirrors.
> "Rick Clark" <[log in to unmask]> wrote in message
> news:F4B1826B1A21D211AEC5006008207AF4043773CE@dogbert.csillc.com...
> > I thought I remember a while back an article in one of the
> HP trade mags
> > that described the process of installation and configuration of HP's
> > Mirrored/iX. Anyone remember such an article and could they
> point me to
> > where I can find a copy? Thanks in advance. Please reply privately.
> >
> >
> > Rick Clark
> > Senior Systems Analyst
> > WW&R
> > Cleveland, Ohio
> >
>
>