Messages in this thread | | | Date | Wed, 30 Oct 2002 23:56:10 +0000 | From | Phillip Lougher <> | Subject | Re: ANNOUNCEMENT: Squashfs released (a highly compressed filesystem) |
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Jeff Garzik wrote: > Phillip Lougher wrote:
> >> 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?
mksquashfs...
> > A r/w compressed filesystem would be darned useful too :) > > Jeff >
A r/w compressed filesystem may be my next project... As a couple of people have mentioned there are compressed r/w filesystems already out there.
As you'll know, there are always tradeoffs with filesystem design, it is very difficult to get as good compression with a r/w fs than with a read only filesystem. I wanted to get maximum compression, and quite a few of the techniques I use rely on its read-only nature.
An append only (i.e. files can be added, but not modified), fs might be a useful compromise. With compressed metadata, any modification of files will inevitably achive different compression ratios, and so modification of metadata/files in place is not an option. Appending modified metadata/data brings you to log-structured (journalling) filesystems and compaction (log cleaning) requirements with consequent loss of compression.
Phillip
> > > >
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