From: Christoph Hellwig <hch@infradead.org>
To: device-mapper development <dm-devel@redhat.com>
Subject: Re: dd to a striped device with 9 disks gets much lower throughput when oflag=direct used
Date: Fri, 27 Jan 2012 03:52:26 -0500 [thread overview]
Message-ID: <20120127085226.GA16520@infradead.org> (raw)
In-Reply-To: <CACyXjPzWjBz0=btbL0Gx_qoxRQs7wy9m=dY1--xL29uszTpmFA@mail.gmail.com>
On Thu, Jan 26, 2012 at 05:06:42PM -0800, Richard Sharpe wrote:
> Why do I see such a big performance difference? Does writing to the
> device also use the page cache if I don't specify DIRECT IO?
Yes. Trying adding conv=fdatasync to both versions to get more
realistic results.
next prev parent reply other threads:[~2012-01-27 8:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-27 1:06 dd to a striped device with 9 disks gets much lower throughput when oflag=direct used Richard Sharpe
2012-01-27 6:54 ` Hannes Reinecke
2012-01-27 8:52 ` Christoph Hellwig [this message]
2012-01-27 15:03 ` Richard Sharpe
2012-01-27 15:16 ` Zdenek Kabelac
2012-01-27 15:28 ` Richard Sharpe
2012-01-27 17:24 ` Zdenek Kabelac
2012-01-27 17:48 ` Richard Sharpe
2012-01-27 18:06 ` Zdenek Kabelac
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