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To: Pieter de Goeje <pieter@degoeje.nl>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Fri, 01 Jan 2010 21:53:43 +0100."
	<201001012153.44349.pieter@degoeje.nl> 
Date: Fri, 01 Jan 2010 22:47:12 +0000
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Cc: Alexander Motin <mav@freebsd.org>, freebsd-current@freebsd.org,
	Miroslav Lachman <000.fbsd@quip.cz>,
	Thomas Backman <serenity@exscape.org>, freebsd-arch@freebsd.org
Subject: Re: File system blocks alignment 
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In message <201001012153.44349.pieter@degoeje.nl>, Pieter de Goeje writes:

>That yielded some pretty spectacular results. [...]
>
>Performance for restore was abysmal in the unaligned case, easily being 10 
>times slower than aligned restore. Newfs was about 5 times as slow.

That is what I expected, only I didn't expect a factor 14 in performance.

I'm not surprised that newfs and restore take the biggest hits in that
test, those are the hard ones, seen from the disk drive, all the read
only work can be cached and "covered up" that way.

Ideally, newfs/UFS should do a quick test to look for any obvious
boundaries, and DTRT, a nice little task for somebody :-)

Poul-Henning

PS: The reason I asked for 3 iterations, was so we could calculate
a standard deviation (See: ministat(8)) in order to have a statistical
sound conclusion.   With a factor 14 in time difference, I will for
once conceede it unnecessary :-)

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.