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Date: Tue, 2 Feb 2010 08:41:35 +0100
From: Jens Axboe <jens.axboe@oracle.com>
Subject: Re: Writing to /dev/null with fio
Message-ID: <20100202074135.GX13771@kernel.dk>
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To: Bart Van Assche <bvanassche@acm.org>
Cc: fio@vger.kernel.org

On Tue, Feb 02 2010, Bart Van Assche wrote:
> Hello Jens,
> 
> I noticed that writing with fio to /dev/null takes much more time (220
> times more for the test below) than with dd. Did I specify the correct
> arguments to fio ? If so, is this known behavior of fio ?
> 
> $ dd if=/dev/zero of=/dev/null bs=1M count=1024
> 1024+0 records in
> 1024+0 records out
> 1073741824 bytes (1.1 GB) copied, 0.121485 s, 8.8 GB/s
> 
> $ fio --bs=1M --size=1G --buffered=1 --rw=write --verify=0
> --name=dev-null /dev/null

You are writing to a file named dev-null and /dev/null is being ignored
as an argument. You want a --filename=/dev/null at the end instead.

-- 
Jens Axboe