Date: Tue, 23 Mar 1999 10:41:45 -0500 From: Doug Ledford <dledford@redhat.com> To: pmanuel@cindy.fe.up.pt Cc: AIC7xxx@FreeBSD.ORG Subject: Re: AIC-7XXX scsi driver optimization Message-ID: <36F7B639.1F94DDF8@redhat.com> References: <Pine.LNX.3.96.990319215205.28758A-100000@cindy.fe.up.pt>
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pmanuel@cindy.fe.up.pt wrote:
>
> Hello all!
>
> I've been playing with a new Linux server and a raid system with a
> couple big (100GB) logical volumes, and after reading the AIC7XXX driver
> documentation i wondered how some of the commands could really affect
> performance on a loaded server. Does anyone have experience tuning those
> parameters? For instance, i believe that enabling tagged queueing on each
> device (now its disabled by default) to a value like 32 could be a good
> idea, but dont know about side effects, of it it is worth it. Anyone has
> real data on it?
With good disks (like Cheetahs) you can see up to a 30% performance
increase on certain tasks by enabling tagged queueing. On other disks,
it might actually get slower. Some disks simply don't like tagged
queueing at all. So, I go the safe route and ship my code with tagged
queueing disabled. You can test it for yourself, and if it likes your
disks, then your in a good position to enable it by default.
--
Doug Ledford <dledford@redhat.com>
Opinions expressed are my own, but
they should be everybody's.
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