Re: Disk Mirroring
From: SuperGumby [SBS MVP] (not_at_your.nellie)
Date: 02/19/04
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Date: Fri, 20 Feb 2004 07:54:51 +1100
are we still discussing disk mirroring? 'coz my only comments about Exchange
IFS are I don't like it and I'm glad that though it is available in Exchange
2003 some sense prevailed and the M: drive is no longer available by
default.
Mirroring is another matter but my thoughts a more general about RAID. It's
a server, it must have RAID. Implement good hardware SCSI RAID if you can or
lousy software RAID if you must.
These days, drives seem to be failing at a much higher rate than as little
as a couple of years ago, particularly IDE drives but also SCSI's. Funnily,
drive manufacturers seem to be quoting higher MTBF rates, I don't believe
them. This is the main reason for including a hotspare in an array.
Something I'd have liked to see in Windows software raid is a better alert
than an inoccuous event log message, something like an alert window popping
on screen and a siren going off would be nice, I'd even tolerate the system
automatically doing a clean shutdown after a short response period. Most
decent SCSI hardware RAID controllers have ear shattering non pure sine wave
(so the sound is really annoying) alarms that go off if the arrray has an
error, this is good. The better ones can email someone as well. Many IDE
RAID controllers either don't have such alarms or rely on software to
perform this function.
SCSI RAID beats IDE 'hands down', every time. The busier the system the more
significant the difference. People can throw idealised test scenarios and
raw throughput equations around as much as they like, the truth of the
pudding is in the eating and I've sat down at older SCSI RAID systems which
outperform newer IDE RAID. I believe this is due to fundamental differences
in SCSI vs IDE drives with 'command queueing' being a major factor.
Something I don't like about hardware RAID controllers. Many cards claiming
to be hardware RAID controllers, most IDE and low end SCSI, are actually
just a card with embedded linux running the array.
OHH, there's another thing I don't like about hardware RAID. The interface,
the human interface. The eggheads who design these things often make the
interface mind bogglingly complex. I consider m'self familiar with both the
concepts and the operation of hardware RAID and I have sat at some and
wondered 'hmmmmm, do I click yes?'
-- Mick Malloy http://www.micropol.com.au "John LeMay" <jlemay@njmc.com> wrote in message news:MPG.1a9ebbfdbe9b2fd8989727@news.individual.net... > In article <eVDr4Gt9DHA.488@TK2MSFTNGP12.phx.gbl>, not@your.nellie > says... > > Wherever possible I avoid converting drives to dynamic, I am yet to see any > > positive effect from doing so and there's a bucketload of reasons why to not > > do it. YES, I HATE dynamic drives. I reckon they're almost as silly an idea > > as making the Exchange database available through IFS, or maybe it's the > > other way around, I reckon both are bloody silly ideas. > > SG, > > Sounds like you have played with these a bit. Any tips or links for > those of us yet to tackle the concept? I just figured the feature acted > like other disk virtualization software (the only thing I can think of > off hand is the Sun disk mirroring software, and we won't get into that > here!). > > -- > John LeMay > kc2kth > Senior Technical Manager > NJMC | http://www.njmc.com | Phone 732-557-4848
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