linux-kernel - Re: Slow disks.

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Date:	Mon, 27 Dec 2010 01:34:56 +0100
From:	Rogier Wolff <R.E.Wolff@...Wizard.nl>
To:	Mark Knecht <markknecht@...il.com>
Cc:	Jeff Moyer <jmoyer@...hat.com>,
	Rogier Wolff <R.E.Wolff@...wizard.nl>,
	Greg Freemyer <greg.freemyer@...il.com>,
	Bruno Prémont <bonbons@...ux-vserver.org>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: Slow disks.

On Sun, Dec 26, 2010 at 03:38:51PM -0800, Mark Knecht wrote:
> First, the drives are 4K sector so it's really important to get them
> on the right partition boundary. Installing Gentoo requires that we
> un-tar some large-ish files. IIRC on a 512 byte boundary these drives
> took 20-30 minutes to do this. On a 4K boundary they took about 1
> minute. I know that doesn't make sense but those were my numbers, and
> it's a very high end Intel i7-980x MB so there wasn't any other
> problem I could find.

Mark, 

Thanks for your contribution. You're seeing a 20-30 fold performance
issue, where only about 2x would be expected. So to test this theory
I'll see if we can evacuate a partition, untar a large-ish file as a
benchmark, and then see if we can improve that by changing the
alignment of the partition. (hmm. Maybe we should do things the other
way around. First find a tar-workload that takes about 1 minute on a
properly working drive, and then we can wait up to 30 minutes for it
to finish on the improper setup.).

Being able to reproduce a problem at will is a great progress to being
able to solve it!

	Roger. 

-- 
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