Squash Fs - Revision history

Tim Bird: /* LZMA */ add info about latest LZMA support submission to mainline

2009-12-09T19:28:16Z

‎LZMA: add info about latest LZMA support submission to mainline

Tim Bird: /* Status/News */ add lnk to news about LZMA support

2009-11-06T23:47:03Z

‎Status/News: add lnk to news about LZMA support

Tim Bird: indicate mainline status

2009-03-06T19:34:03Z

indicate mainline status

Kaa-ching at 01:09, 4 December 2008

2008-12-04T01:09:25Z

TimBird: /* File System Performance */ fix lnk to comparisons page

2008-06-25T18:44:45Z

‎File System Performance: fix lnk to comparisons page

Chris at 02:37, 16 July 2007

2007-07-16T02:37:45Z

Wmat: /* How To Use */

2006-12-15T18:43:54Z

‎How To Use

Wmat: Legacy Content Conversion

2006-12-15T18:42:44Z

Legacy Content Conversion

New page

== Description ==
"Squash FS" is the name of a compressed read-only filesystem for Linux. There are a number of such file systems available for Linux, including ROMFS, CRAMFS and SquashFS.

== Rationale ==
A compressed file system is interesting in embedded systems for reducing the overall size (in flash) of the Linux system. Squash FS is reported to have better compression capabilities than CRAMFS, which is a very popular

== Resources ==
=== Projects ===
The Squash fs home page is at: [http://squashfs.sourceforge.net/ Squash FS]

=== Specifications ===
There are no specifications on this technology.

== Downloads ==
=== Patch ===
*see the Squash fs [http://sourceforge.net/project/showfiles.php?group_id=63835 download page] for latest patches

=== Utility programs ===
The squashfs file release contains a README, the squashfs patch files, and the squashfs-tools directory (mksquashfs). Please see the INSTALL file for install instructions.

== How To Use ==
See the Squash FS Howto:
[http://artemio.net/projects/linuxdoc/squashfs online version]
[[Squash Fs Howto]] page (copy of document in this wiki - may be out of date)

== Sample Results ==

Here are brief summaries for 2 large file systems, saved using a variety of file system types.

This information was provided by Phillip Lougher.

=== Ubuntu liveCD compression results ===

<pre>
ext3 uncompressed size 1.4 GB
ISO9660 uncompressed size 1.3 GB
Zisofs compressed size 589.81 MB
Cloop compressed size 471.89 MB
Squashfs2.0 compressed size 448.58 MB
Squashfs2.1 compressed size 448.58 MB
</pre>

=== Damn Small Linux liveCD compression results ===

<pre>
ext3 uncompressed size 126 MB
CRAMFS compressed size 52.19 MB
Squashfs2.0 compressed size 46.52 MB
Squashfs2.1 compressed size 46.52 MB
</pre>

=== File System Performance ===
There is performance data for these file systems on the page SquashFsComparisons.

=== lzma data comparison ===
Here is some information that was posted recently on the squashfsmailing list by Oleg Vdovikin:

<pre>
> # du -s target
> 7836 target
> # ls -l target.*
> -rw-r--r-- 1 root root 2842788 Aug 27 17:54 target.cramfs
> -rwx------ 1 root root 2449408 Jan 26 13:19 target.sqshfs
> -rwx------ 1 root root 2060288 Jan 26 13:21 target.lzmafs
>
> So, lzma for this filesystem gives 84% of original size. For bigger
> filesystem I've got 82%.
</pre>

= Future Work/Action Items =
Here is a list of things that could be worked on for this feature:
*there was a report in August, 2004 of problems with squashfs on PPC. see [http://sourceforge.net/forum/message.php?msg_id=2735613 here] (at bottom of page)
*there was a suggestion to use LZMA compression for version 3.0 of squashfs - see [http://sourceforge.net/forum/forum.php?thread_id=1113639&forum_id=215699 here]

== Notes on compression ==
<pre>
From: John Richard Moser <nigele...@comcast.net>
Date: Wed, 29 Sep 2004 18:20:11 +0200
Subject: Re: Compressed filesystems: Better compression?

Matti Aarnio wrote:
| Compression algorithms are a bit tough to be used in a random access
| smallish blocks environments. In long streams where you can use megabytes
| worth of buffer spaces there is no problem is achieving good performance.
| But do try to do that in an environment where your maximum block size
| is, say: 4 kB, and you have to start afresh at every block boundary.

Yes of course. I've seen the compressed page cache patch do this and
get fair peformance (10-20%), though on double size blocks (8KiB) it
manages almost twice as good (20-50%, averaged around 30% IIRC). Not
great, but not bad.

On compressed filesystems you can work with 64k or 128k blocks.
Somewhere around 32-64k is usually optimal; you're not going to see
great improvements using 1M blocks instead of 512k blocks.

| Whatever algorithms you use, there will always be data sequences that
| are of maximum entropy, and won't compress. Rather they will be
| presented in streams as is with a few bytes long wrappers around
| them.

Yes, an intelligent algorithm decides that if the underlying compression
algorithm used produces no results, it just marks the block as
uncompressed and stores it as such. ZLIB does this if the block gets
bigger. LZMA might not; but higher level intrinsics (block headers)
could handle that easy (as you said).
</pre>

@@ Line 63: / Line 63: @@
 == LZMA ==
 Disadvantages:
-* the LZMA algorithm is not in the kernel yet
+* Decompression is slower than zlib
-* decompression is slower than zlib
 === lzma data comparison ===

@@ Line 13: / Line 13: @@
 http://lwn.net/Articles/314326/ and the kernel change log at:
 http://kernel.org/pub/linux/kernel/v2.6/testing/ChangeLog-2.6.29-rc1
 == Downloads ==

← Older revision		Revision as of 02:37, 16 July 2007
Line 106:		Line 106:
	could handle that easy (as you said).		could handle that easy (as you said).
	</pre>		</pre>
		+
		+	[[Category:File Systems]]

@@ Line 7: / Line 7: @@
 == Resources ==
 === Projects ===
-The Squash fs home page is at: [http://squashfs.sourceforge.net/ Squash FS]
+The SquashFS home page is at: [http://squashfs.sourceforge.net/ Squash FS]
-=== Specifications ===
+== Status/News ==
-There are no specifications on this technology.
+SquashFS version 4.0 was accepted into the mainline kernel in January 2009.  See
 == Downloads ==
 === Patch ===
-* see the Squash fs [http://sourceforge.net/project/showfiles.php?group_id=63835 download page] for latest patches
+* See the Squash fs [http://sourceforge.net/project/showfiles.php?group_id=63835 download page] for patches
 * if you want LZMA support, read below
 === Utility programs ===

@@ Line 1: / Line 1: @@
 == Description ==
-"Squash FS" is the name of a compressed read-only filesystem for Linux. There are a number of such file systems available for Linux, including ROMFS, CRAMFS and SquashFS.
+"Squash FS" is the name of a compressed read-only filesystem for Linux. There are a number of such file systems available for Linux, including ROMFS, [[File_Systems#CramFS | CramFS]] and SquashFS.
 == Rationale ==
-A compressed file system is interesting in embedded systems for reducing the overall size (in flash) of the Linux system.  Squash FS is reported to have better compression capabilities than CRAMFS, which is a very popular
+A compressed file system is interesting in embedded systems for reducing the overall size (in flash) of the Linux system.  Squash FS is reported to have better compression capabilities than CramFS, which is a very popular.
 == Resources ==
@@ Line 14: / Line 14: @@
 == Downloads ==
 === Patch ===
-*see the Squash fs [http://sourceforge.net/project/showfiles.php?group_id=63835 download page] for latest patches
+* see the Squash fs [http://sourceforge.net/project/showfiles.php?group_id=63835 download page] for latest patches
 === Utility programs ===
@@ Line 52: / Line 54: @@
 === File System Performance ===
 There is performance data for these file systems on the page [[Squash Fs Comparisons]]
 === lzma data comparison ===
-Here is some information that was posted recently on the squashfsmailing list by Oleg Vdovikin:
+Here is some information that was posted recently (?) on the squashfs mailing list by Oleg Vdovikin:
 <pre>
@@ Line 68: / Line 79: @@
 </pre>
-== Notes on compression ==
+=== Notes on compression ===
 <pre>
 From: John Richard Moser <nigele...@comcast.net>
@@ Line 106: / Line 113: @@
 could handle that easy (as you said).
 </pre>
 [[Category:File Systems]]

@@ Line 21: / Line 21: @@
 == How To Use ==
 See the Squash FS Howto:
-[http://artemio.net/projects/linuxdoc/squashfs online version]
+*[http://artemio.net/projects/linuxdoc/squashfs online version]
-[[Squash Fs Howto]] page (copy of document in this wiki - may be out of date)
+*[[Squash FS Howto]] page (copy of document in this wiki - may be out of date)
 == Sample Results ==