Date: Wed, 28 Feb 1996 00:00:16 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: terry@lambert.org (Terry Lambert) Cc: jfieber@indiana.edu, jerry@border.com, jkh@time.cdrom.com, hackers@FreeBSD.ORG Subject: Re: OK, so what would YOU like to see on that second CD? Message-ID: <199602272300.AAA04556@labinfo.iet.unipi.it> In-Reply-To: <199602272049.NAA05743@phaeton.artisoft.com> from "Terry Lambert" at Feb 27, 96 01:48:58 pm
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> I have some example file compression code for the Heidemann framework; > John has asked that I not redistribute it. but the problem is not the compression code, there's plenty of it out there, and some is even reasonably fast [and often the same algorithm has been patented several times by different people, *after* an implementation was made available on the net; I was reading the comp.compression FAQ the other night and it's full of this kind of stories! ]. The problem is that compressed blocks have variable size, and handling them efficiently requires (I believe) big changes in the device+fs code. Perhaps log-structured filesystems lend themselves better to this. > It would be trivial to implement block compression at the device export > layer in the devie framework I suggested previously. This is similar while you can certainly make a compressed device look like a regular one, I believe some efficiency is lost, and not only because of compression. The FS layout assumes that adjacent blocks are adjacent (modulo a few bad sectors). But what on a compressed device ? Luigi ==================================================================== Luigi Rizzo Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it Universita' di Pisa tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ ====================================================================
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