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Date:      Tue, 04 Sep 2001 10:06:19 +0100
From:      Pete French <pfrench@firstcallgroup.co.uk>
To:        behanna@zbzoom.net, grog@FreeBSD.org
Cc:        stable@FreeBSD.ORG
Subject:   Re: RAID5
Message-ID:  <E15eC9z-0003e5-00@mailhost.firstcallgroup.co.uk>
In-Reply-To: <20010904105035.C10292@wantadilla.lemis.com>

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> Interestingly, CPU isn't the performance issue most people (myself
> once included) assume it is.  Even on my original Vinum testbed, a
> 468/66, CPU usage was barely measurable.  That's probably why most
> hardware RAID controllers use relatively slow CPUs.

Interesting comment. I have acciddentally acquired apair of SMART 2SL
controllers. One of which I am using as the boot device for the FreeBSD
box (because iits theonly disc controller I've got - RAID 0). The other
I was going to use to build an array, but I am having trouble finding any
comoparative benchmarks as to how slow certain combinations of drives
are under RAID-5. Are their certain numbers that make the processing "easier"
for the onboard chip ? (*i.e. does 5 discs make life for it faster as it
can split a byte onto 4 platters and allocate one for parity rather than
dooing shifts all over the place ?) or is it best to just give it as many
dricves as possible (8 in this case).

-pcf.

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