Date: Mon, 25 Oct 2004 23:39:57 +0200 From: Brad Knowles <brad@stop.mail-abuse.org> To: Scott Long <scottl@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: FreeBSD 5.3b7and poor ata performance Message-ID: <p06002061bda3224cd029@[10.0.1.3]> In-Reply-To: <417D6F4C.9000404@freebsd.org> References: <14479.1098695558@critter.freebsd.dk><417D25E8.6080804@ng.fadesa .es> <200410251928.01536.victor@alf.dyndns.ws><200410251837.58257.Thoma s.Sparrev ohn@btinternet.com><417D3F12.20302@DeepCore.dk> <417D40A1.9030802@ng.fadesa.es><417D45F1.9090504@freebsd.org> <77F3FD4D-26BE-11D9-9A2F-003065ABFD92@mac.com><417D58B6.5030509@fr eebsd.org > <F5F15CA0-26C5-11D9-9A2F-003065ABFD92@mac.com> <417D65F1.2040809@freebsd.org> <p0600205fbda318006656@[10.0.1.3]> <417D6F4C.9000404@freebsd.org>
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At 3:25 PM -0600 2004-10-25, Scott Long wrote:
> But as was said, there is always
> a performance vs. reliability tradeoff.
Well, more like "Pick two: performance, reliability, price" ;)
> And when you are talking about
> RAID-10 with a bunch of disks, you will indeed start seeing bottlenecks
> in the bus.
When you're talking about using a lot of disks, that's going to
be true for any disk subsystem that you're trying to get a lot of
performance out of.
The old rule was that if you had more than four disks per
channel, you were probably hitting saturation. I don't know if that
specific rule-of-thumb is still valid, but I'd be surprised if disk
controller performance hasn't roughly kept up with disk performance
over time.
--
Brad Knowles, <brad@stop.mail-abuse.org>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/>; for more info.
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