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Date: Fri, 27 Oct 2006 22:03:06 -0400
From: Martin Cracauer <cracauer@cons.org>
To: "Kenneth D. Merry" <ken@kdm.org>
Message-ID: <20061028020306.GA93408@cons.org>
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Cc: freebsd-scsi@freebsd.org, Martin Cracauer <cracauer@cons.org>
Subject: Re: Why is SCSI so much faster with the write cache off (than ATA)?
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Kenneth D. Merry wrote on Fri, Oct 27, 2006 at 04:04:50PM -0600: 
> 10 years ago, ATA disks didn't do tagged queueing, but SCSI disks did.  

I actually had used some of the rare IBM drives and the Intel 440BX
chipset that did support it at the time.  But some bit must have been
missing.

> Now, SATA disks have tagged queueing and also NCQ.  In theory those should
> work well.  Is tagged queueing enabled on the ATA disks you're testing?  Is
> it the old-style queueing or NCQ?

I was done on an NVidia SATA controller, so neither would be available.

Very interesting.  Now that I think about it all makes sense.  Thanks,
guys.

Martin
-- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Martin Cracauer <cracauer@cons.org>   http://www.cons.org/cracauer/
FreeBSD - where you want to go, today.      http://www.freebsd.org/