Date: Fri, 1 Jan 2010 17:03:03 -0700 From: Scott Long <scottl@samsco.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Alexander Motin <mav@freebsd.org>, Miroslav Lachman <000.fbsd@quip.cz>, Thomas Backman <serenity@exscape.org>, freebsd-current@freebsd.org, freebsd-arch@freebsd.org, Pieter de Goeje <pieter@degoeje.nl> Subject: Re: File system blocks alignment Message-ID: <925A0DA7-5D9B-41FA-B586-6C128F816C58@samsco.org> In-Reply-To: <65036.1262386032@critter.freebsd.dk> References: <65036.1262386032@critter.freebsd.dk>
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On Jan 1, 2010, at 3:47 PM, Poul-Henning Kamp wrote: > 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. > It's all about read latency in the read-modify update operation. While buses and caches and gotten steadily faster over the past 20 years, disk platters and hysteresis fields have not. This is also why buying faster platters is always an important consideration for overall performance; a desktop or laptop with 5400RPM drives will feel significantly slower than one with 7200RPM drives, and 15K RPM drives still rule the roost. Thanks a lot for doing the testing. Would it be possible to publish these results somewhere that can be linked to in the future? Scott
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