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List:       linux-kernel
Subject:    Re: ANNOUNCEMENT: Squashfs released (a highly compressed filesystem)
From:       Jeff Garzik <jgarzik () pobox ! com>
Date:       2002-10-30 4:03:20
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Phillip Lougher wrote:

> Samuel Flory wrote:
>
>> Phillip Lougher wrote:
>>
>>> 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.
>>>
>>
>>  What are the advantages of squashfs vs cramfs?
>>
>>
>>
>
> Cramfs was the inspiration for squashfs.  Squashfs basically gives 
> better compression, bigger files/filesystem support, and more inode 
> information.
>
> 1. Blocks upto 32K are supported - data is compressed in units of 32K 
> which achieves better compression ratios than compressing in 4K 
> blocks.  Generally using bigger than 4K blocks are a bad idea, because 
> the VFS calls the filesystem in 4K pages.  Squashfs explictly pushes 
> the extra block data into the page cache.

I'm curious if you looked at ntfs-tng's code before implementing this. 
 It's pretty darned optimal...

> 2. Squashfs compresses inode and directory information in addition to 
> file data.  Inodes/directories generally compress down to 50%, or say 
> on average 8 bytes or less per inode.

squashfs or mksquashfs?

A r/w compressed filesystem would be darned useful too :)

    Jeff




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