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* ANNOUNCEMENT: Squashfs released (a highly compressed filesystem)
@ 2002-10-30  2:29 Phillip Lougher
  2002-10-30  3:10 ` Samuel Flory
  0 siblings, 1 reply; 17+ messages in thread
From: Phillip Lougher @ 2002-10-30  2:29 UTC (permalink / raw)
  To: linux-kernel

Hi,

First release of squashfs.  Squashfs is a highly compressed read-only 
filesystem for Linux (kernel 2.4.x).  It uses zlib compression to 
compress both files, inodes and directories.  Inodes in the system are 
very small and all blocks are packed to minimise data overhead. Block 
sizes greater than 4K are supported up to a maximum of 32K.

Squashfs is intended for general read-only filesystem use, for archival 
use, and in embedded systems where low overhead is needed.

Squashfs is available from http://squashfs.sourceforge.net.

The patch file is currently against 2.4.19.  There is further info on 
the filesystem design etc. in the README.

I'l be interested in getting any feedback, advice etc. on it.

Phill Lougher


^ permalink raw reply	[flat|nested] 17+ messages in thread
* Re: ANNOUNCEMENT: Squashfs released (a highly compressed filesystem)
@ 2002-10-30 14:17 Matthew Wilcox
  0 siblings, 0 replies; 17+ messages in thread
From: Matthew Wilcox @ 2002-10-30 14:17 UTC (permalink / raw)
  To: Larry McVoy; +Cc: linux-kernel

Larry McVoy wrote:
> > A r/w compressed filesystem would be darned useful too :)
> 
> mmap(2) is, err, hard. Not impossible, it means the file system has to
> support both compressed and uncompressed files, but it's interesting.

Easier than you think, perhaps.  Depends how much compression you're
after, of course, but here's how Acorn did it in RISCiX (a 4.3BSD
derivative):

Pages were 32k (an interesting feature of the MMU...), and the underlying
filesystem was a fairly vanilla BSD FFS (probably 4k blocks with 1k
fragments; discs were around 50MB).  Each page was written at a 32k
boundary, but compressed.  So there were holes in the file where other
files could store their data.  Naturally you waste on average 512 bytes
per 32k page, but I think they managed to get 80MB of unix distro onto
a 50MB disc this way, so it's nothing to be sneezed at.

-- 
Revolutions do not require corporate support.

^ permalink raw reply	[flat|nested] 17+ messages in thread
* Re: ANNOUNCEMENT:  Squashfs released (a highly compressed filesystem)
@ 2002-10-31  5:12 Phillip Lougher
  0 siblings, 0 replies; 17+ messages in thread
From: Phillip Lougher @ 2002-10-31  5:12 UTC (permalink / raw)
  To: willy; +Cc: linux-kernel

Matthew Wilcox wrote:
 >Larry McVoy wrote:
 >> > A r/w compressed filesystem would be darned useful too :)
 >> > mmap(2) is, err, hard. Not impossible, it means the file system 
has >to
 >> support both compressed and uncompressed files, but it's interesting.
 >
 >Easier than you think, perhaps.  Depends how much compression you're
 >after, of course, but here's how Acorn did it in RISCiX (a 4.3BSD
 >derivative):
 >

Strange you should mention this... I used to work at Acorn with
the guy who did this (Mark Taunton). RISCiX was too early to be 4.3, I
think it was 4.1, but may have been 4.2, certainly no later, this was
1989.

 >Pages were 32k (an interesting feature of the MMU...), and the 
 >underlying filesystem was a fairly vanilla BSD FFS (probably 4k blocks
 >with 1k fragments; discs were around 50MB).  Each page was written at 
a >32k boundary, but compressed.  So there were holes in the file where 
 >other files could store their data.  Naturally you waste on average 
512 >bytes per 32k page, but I think they managed to get 80MB of unix 
distro >onto a 50MB disc this way, so it's nothing to be sneezed at.

They only needed to compress the fs on the R140 (an ARM 2 based
machine).  The better R260 had a bigger disk, and so didn't need the
compression. Interestingly, because of the slow disk I/O, compression
made the filesystem access faster.

I had an R140, and space was so tight in the filesystem, you had
to delete part of the distribution before you could even compile
a program!

Phillip


^ permalink raw reply	[flat|nested] 17+ messages in thread
end of thread, other threads:[~2002-11-02  8:56 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2002-10-30  2:29 ANNOUNCEMENT: Squashfs released (a highly compressed filesystem) Phillip Lougher
2002-10-30  3:10 ` Samuel Flory
2002-10-30  3:51   ` Phillip Lougher
2002-10-30  4:03     ` Jeff Garzik
2002-10-30  4:11       ` Larry McVoy
2002-10-30  4:15         ` Jeff Garzik
2002-10-30 14:53         ` Jesse Pollard
2002-10-30 15:10           ` Padraig Brady
2002-10-30 15:42             ` Denis RICHARD
2002-10-31 16:18               ` Nicholas Wourms
2002-10-30 23:56       ` Phillip Lougher
2002-11-01 15:57         ` Rob Landley
2002-11-02  8:57           ` Phillip Lougher
2002-10-30  6:28     ` Ingo Oeser
2002-10-31  4:08       ` Phillip Lougher
  -- strict thread matches above, loose matches on Subject: below --
2002-10-30 14:17 Matthew Wilcox
2002-10-31  5:12 Phillip Lougher

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