From: Mark Lord <lkml@rtr.ca>
To: Phillip Susi <psusi@cfl.rr.com>
Cc: Chris Snook <csnook@redhat.com>, Paa Paa <paapaa125@hotmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: Lower HD transfer rate with NCQ enabled?
Date: Wed, 04 Apr 2007 11:36:50 -0400 [thread overview]
Message-ID: <4613C612.5040600@rtr.ca> (raw)
In-Reply-To: <4612A854.1070702@cfl.rr.com>
Phillip Susi wrote:
> Mark Lord wrote:
>> But WD drives, in particular the Raptor series, have a firmware "feature"
>> that disables "drive readahead" whenever NCQ is in use.
>
> Why is this an issue? Shouldn't the kernel be sending down its own
> readahead requests to keep the disk busy?
The drive firmware readahead is inherently *way* more effective than
other forms, and without it, sequential read performance really suffers.
Regardless of how software tries to compensate.
This is mostly a problem with the WD Raptor drive, and some other WD drives.
I have not yet encountered/noticed the problem with other brands.
-ml
next prev parent reply other threads:[~2007-04-04 15:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-03 7:11 Lower HD transfer rate with NCQ enabled? Paa Paa
2007-04-03 9:18 ` Nick Piggin
2007-04-03 21:31 ` Paa Paa
2007-04-04 2:06 ` Nick Piggin
2007-04-06 21:33 ` Bill Davidsen
2007-04-03 16:31 ` Chris Snook
2007-04-03 16:47 ` Mark Lord
2007-04-03 19:17 ` Phillip Susi
2007-04-04 15:36 ` Mark Lord [this message]
2007-04-05 15:30 ` Phillip Susi
2007-04-05 16:11 ` Mark Lord
2007-04-05 16:45 ` Lennart Sorensen
2007-04-09 14:46 ` Phillip Susi
2007-04-10 3:58 ` Mark Lord
-- strict thread matches above, loose matches on Subject: below --
2007-04-05 16:26 Paa Paa
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