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Message-ID: <5699f8f00711030244j4d8bed83j3a9e4a2191201a3c@mail.gmail.com>
Date: Sat, 3 Nov 2007 10:44:14 +0100
From: "Wander Winkelhorst" <w.winkelhorst@gmail.com>
To: "Rik van Riel" <riel@surriel.com>
Subject: Re: WANTED: kernel projects for CS students
Cc: Valdis.Kletnieks@vt.edu, "Lennart Sorensen" <lsorense@csclub.uwaterloo.ca>,
       "Pavel Machek" <pavel@ucw.cz>, linux-kernel@vger.kernel.org
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On 11/3/07, Rik van Riel <riel@surriel.com> wrote:
> On Fri, 02 Nov 2007 23:08:23 -0400
> Valdis.Kletnieks@vt.edu wrote:
>
> > IBM's AIX supported file system compression on the JFS filesystem
> > years ago. I was able to get up to 30% throughput increases by
> > converting the /usr filesystem to compressed - because even a 33mhz
> > Power chipset could read in 5 512-byte blocks and decompress it to
> > the original 4K faster than the disk could read in 8 512-byte
> > blocks.
>
> > Given that today there's an even *bigger* disparity in CPU speed
> > versus disk speed, I'd be surprised if it doesn't help today too.
>
> The problem is that disk seek times have not gotten much
> faster over the years, while disk throughput rates have
> skyrocketed.
>
> Transferring a little less data is not going to help you
> when 80% of your disk time is spent seeking, not reading
> or writing.

This sounds like flash based media are an ideal candidate for compression.
No seek times to speak of, transfer rates that are lower than those of
disks and limited capacity.

I believe JFFS2 (a flash filesystem) allready does compression though.
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