linux-kernel - Re: xfs: does mkfs.xfs require fancy switches to get decent performance? (was Tux3 Report: How fast can we fsync?)

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Message-ID: <20150511231714.GD14088@thunk.org>
Date:	Mon, 11 May 2015 19:17:14 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Pavel Machek <pavel@....cz>
Cc:	Daniel Phillips <daniel@...nq.net>, Howard Chu <hyc@...as.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tux3@...3.org, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: xfs: does mkfs.xfs require fancy switches to get decent
 performance? (was Tux3 Report: How fast can we fsync?)

On Tue, May 12, 2015 at 12:12:23AM +0200, Pavel Machek wrote:
> Umm, are you sure. If "some areas of disk are faster than others" is
> still true on todays harddrives, the gaps will decrease the
> performance (as you'll "use up" the fast areas more quickly).

It's still true.  The difference between O.D. and I.D. (outer diameter
vs inner diameter) LBA's is typically a factor of 2.  This is why
"short-stroking" works as a technique, and another way that people
doing competitive benchmarking can screw up and produce misleading
numbers.  (If you use partitions instead of the whole disk, you have
to use the same partition in order to make sure you aren't comparing
apples with oranges.)

Cheers,

					- Ted
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