"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 12/28/2005
01:02:49 PM:
> On the HP and the IBM 3583 we see drive failures approximately every two
> months. We have had occasions where as many as three different drives
> have failed in a single week. Only the 3575s have avoided that failure
> frequency; with them it's about one drive failure per year.
IBM 3494 libraries are a shining example of this rule; there's a reason
they're so expensive. In *my* dream shop, it's IBM 3575 libraries (now
sadly out of production!) for their *very* fast access, and the IBM 3494
for the heavyweight work. I think of them as quarterhorses and
Clydesdales.
Large STK boxes (like the PowderHorn) are capable of true enterprise work,
but I don't much like their drive failure rates. If 1/20 of my drive set
fails or balks every month, that's too much.
> If you take a step back and look at the big picture, it's that - in my
> opinion - the commercial quality tape drives are simply not designed for
> the pounding they get from an enterprise backup system like TSM. I'm
> confident that users of Veritas, etc. will report similar failure rates.
> When I've reported to HP Tech Support that "their" library receives 250
GB
> a day they exclaimed "Wow!". Imagine if you're one of the forum
> participants who sends TBs/day to the tapes.
(I move more than 250GB/day/drive, and I've got a lot of drives.)
For small shops (< 250GB/day), 3583s and smaller STK 9840 libraries work
well along as long as they can work less than 8 hours a day.
> Symptom-wise, what we see is this:
> - LTO: mount/dismount failures.
I like the LTO's forward-looking technology, but I just don't think
they're *quite* ready for the enterprise-scaled Big Leagues. LTO-3s are
finally getting the access time needed for the future, but the furbishing
things take too darn long to seek through 800GB of tape to find one 3K
file!
Wish the LinearTapeOpen folks hadn't abadoned the twin-spindled Accellis
idea.
Let's face it--mass disk storage, with offsite tape, is the way
everything's going.
> - DLT: mount failures and poor performance; first sign of a drive
wearing
> out is its throughput drops to 10% of its normal rate.
DLTs are for very small daily throughputs and admins who don't mind
babying their hardware.
> - The few 3570 failures we've had usually caused dismount failures.
>
> Just my two cents.
Naw, it's worth more than that--good advice, as the punchline in
MasterCard commercials claims, is priceless.
--
Mark Stapleton (mark.stapleton AT usbank DOT com)
MR Backup and Recovery Management
U.S. Bank
Office 262.790.3190
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