From: "Jakob Østergaard" <jakob@unthought.net>
To: Chris Friesen <chris_friesen@sympatico.ca>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: software raid issues -- possible kernel I/O problem?
Date: Sun, 9 Dec 2001 20:19:00 +0100 [thread overview]
Message-ID: <20011209201900.A8549@unthought.net> (raw)
In-Reply-To: <3C11358D.28400117@sympatico.ca> <3C114539.62A0D8E7@sympatico.ca>
In-Reply-To: <3C114539.62A0D8E7@sympatico.ca>; from chris_friesen@sympatico.ca on Fri, Dec 07, 2001 at 05:39:53PM -0500
On Fri, Dec 07, 2001 at 05:39:53PM -0500, Chris Friesen wrote:
>
> A number of people have privately pointed out that hdparm -T doesn't
> actually go to the disk at all. Guess I should RTFM...I though that
> this was reading from the disk's cache, not linux's cache. Oops.
>
> I'm still kind of curious why raid-1 reads don't seem to get any
> performance increase over reads from a single disk. Any ideas?
For one single large sequential read, the current RAID-1 code will
not show any significant benefit over the single-disk case.
However, if you read many smaller files, or have multiple concurrent
readers, you should see a good speedup.
Try running two bonnies at the same time.
--
................................................................
: jakob@unthought.net : And I see the elder races, :
:.........................: putrid forms of man :
: Jakob Østergaard : See him rise and claim the earth, :
: OZ9ABN : his downfall is at hand. :
:.........................:............{Konkhra}...............:
next prev parent reply other threads:[~2001-12-09 19:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-07 21:33 software raid issues -- possible kernel I/O problem? Chris Friesen
2001-12-07 22:39 ` Chris Friesen
2001-12-09 19:19 ` Jakob Østergaard [this message]
2001-12-09 19:32 ` Roy Sigurd Karlsbakk
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