From: Mark Lord <liml@rtr.ca>
To: Tejun Heo <htejun@gmail.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>,
Richard Scobie <r.scobie@clear.net.nz>,
linux-ide@vger.kernel.org, Jens Axboe <jens.axboe@oracle.com>
Subject: Re: SAS v SATA interface performance
Date: Mon, 10 Dec 2007 11:32:57 -0500 [thread overview]
Message-ID: <475D6A39.3080909@rtr.ca> (raw)
In-Reply-To: <475CEBBA.3050409@gmail.com>
Tejun Heo wrote:
..
> NCQ is not more advanced than SCSI TCQ. NCQ is "native" and "advanced"
> compared to old IDE style bus-releasing queueing support which was one
> ugly beast which no one really supported well. The only example I can
> remember which actually worked was first gen raptors paired with
> specific controller with custom driver on windows.
..
I wrote PATA drivers for some chipsets that had hardware support for TCQ,
and it did make a very impressive throughput difference when enabled.
The IBM/Hitachi Deathst.. err.. Deskstar.. drives always had the best
support in firmware. I believe we also used some WD drives, though there
firmware didn't perform as well.
ISTR that NCQ wins over TCQ (ATA) because multiple drives can interleave
their data transfers on the bus -- with TCQ, a drive took over the bus
at the start of data transfer and never released it until the command completed.
Cheers
next prev parent reply other threads:[~2007-12-10 16:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-30 19:19 SAS v SATA interface performance Richard Scobie
2007-11-30 21:24 ` Michael Tokarev
2007-11-30 23:17 ` Alan Cox
2007-12-01 7:43 ` Richard Scobie
2007-12-01 14:37 ` Greg Freemyer
2007-12-01 19:19 ` Richard Scobie
2007-12-01 20:01 ` Mark Lord
2007-12-01 20:40 ` Jeff Garzik
2007-12-01 23:55 ` Richard Scobie
2007-12-02 3:45 ` Mark Lord
2007-12-02 3:49 ` Mark Lord
2007-12-10 7:33 ` Tejun Heo
2007-12-10 14:36 ` Jens Axboe
2007-12-10 16:28 ` Mark Lord
2007-12-10 14:50 ` James Bottomley
2007-12-10 16:32 ` Mark Lord [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-12-01 0:04 Richard Scobie
2007-12-01 0:17 ` Alan Cox
2007-12-01 3:06 ` Mark Lord
2007-12-10 7:15 ` Tejun Heo
2007-12-10 16:23 ` Mark Lord
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