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From: Chris Mason <mason@suse.com>
To: linux-lvm@sistina.com
Cc: Andrew Theurer <habanero@us.ibm.com>,
	Kevin Corry <corryk@us.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [Announce] device-mapper beta3 (fast snapshots)
Date: 16 Jul 2002 13:27:24 -0400	[thread overview]
Message-ID: <1026840444.21656.544.camel@tiny> (raw)
In-Reply-To: <20020716163157.GA11334@fib011235813.fsnet.co.uk>

On Tue, 2002-07-16 at 12:31, Joe Thornber wrote:

> > Joe, are you absolutely sure these tests had the disk cache disabled?  That's
> > the only hardware thing I can think of that would make a difference.
> 
> Absolutely sure.  Those figures were for a pair of PVs that were
> sharing an IDE cable so I can certainly get things moving faster.

Some IDE drives ignore commands to turn off the write back cache, or
turn it back on when load gets high.

Try iozone -s 50M -i 0 -o with writeback on and off.  If you get the
same answer the benchmarks are suspect....

-chris



  reply	other threads:[~2002-07-16 17:24 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-07-12 23:21 [Announce] device-mapper beta3 (fast snapshots) Andrew Theurer
2002-07-15  8:59 ` Joe Thornber
2002-07-15 14:39   ` Andrew Theurer
2002-07-15 12:40 ` Joe Thornber
2002-07-15 18:56   ` [linux-lvm] " Kevin Corry
2002-07-16  8:42     ` Joe Thornber
2002-07-16 16:05       ` Andrew Theurer
2002-07-16 16:31         ` Joe Thornber
2002-07-16 17:27           ` Chris Mason [this message]
2002-07-17 10:31             ` Joe Thornber
2002-07-17 11:46               ` Alan Cox
  -- strict thread matches above, loose matches on Subject: below --
2002-05-22 12:51 Joe Thornber

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