From: "Stephen C. Tweedie" <sct@redhat.com>
To: Martin Rauh <martin.rauh@gmx.de>
Cc: linux-kernel@vger.kernel.org, Stephen Tweedie <sct@redhat.com>
Subject: Re: Writing on raw device with software RAID 0 is slow
Date: Thu, 1 Mar 2001 12:14:18 +0000 [thread overview]
Message-ID: <20010301121418.A7647@redhat.com> (raw)
In-Reply-To: <3A9D1202.9A1C403E@gmx.de>
In-Reply-To: <3A9D1202.9A1C403E@gmx.de>; from martin.rauh@gmx.de on Wed, Feb 28, 2001 at 03:58:11PM +0100
Hi,
On Wed, Feb 28, 2001 at 03:58:11PM +0100, Martin Rauh wrote:
>
> Writing to an software RAID 0 containing 4 SCSI discs is very fast.
> I get transfer rates of about 100 MBytes/s. The filesystem on the RAID
> is ext2.
>
> Writing to the same RAID directly (that means on the raw device without
> a filesystem) works
> but gives low transfer rates of about 31 MBytes/s.
>
> Any explanation for that?
Raw IO is always synchronous: it gets flushed to disk before the write
returns. You don't get any write-behind with raw IO, so the smaller
the blocksize you write in, the slower things get.
--Stephen
next prev parent reply other threads:[~2001-03-01 12:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-28 14:58 Writing on raw device with software RAID 0 is slow Martin Rauh
2001-03-01 12:14 ` Stephen C. Tweedie [this message]
2001-03-01 15:44 ` Ben LaHaise
2001-03-01 16:02 ` Stephen C. Tweedie
2001-03-01 16:08 ` Ben LaHaise
2001-03-01 16:29 ` Stephen C. Tweedie
-- strict thread matches above, loose matches on Subject: below --
2001-03-01 16:47 Douglas Gilbert
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