On 2010-09-01 11:04, Per Jessen wrote:
Dave Howorth wrote:
A compressed filesystem? squashfs?
Sorry, don't know much about the field.
Thanks Dave - it's a valid suggestion. I've already looked at squashfs and I may have to take another look, but I think the problem was in the mount time as well as in single-file extraction/retrieval time.
A compressed filesystem is indeed interesting for email. The only only I tested is zisofs, used to create compressed CD/DVDs, directly mountable in linux - ie, access to a single file is direct. However, it does not seem very fast. And the creation is cumbersome. squashfs is also RO. The wikipedia says it uses gzip compression (lzma projected). http://en.wikipedia.org/wiki/Squashfs ]> SquashFS is used by the Live CD versions of Arch Linux, Debian, Fedora, Gentoo Linux, Ubuntu and on embedded distributions such as the OpenWRT and DD-WRT router firmware. It is often combined with a union mount filesystem, such as UnionFS or aufs, to provide a read-write environment for live Linux distributions. This takes advantage of both the SquashFS's high speed compression abilities with the ability to alter the distribution while running it from a live CD. Distributions such as Slax, Debian Live, Mandriva One and Puppy Linux use this combination. ]> ]> The on-disk format of SquashFS has stabilized enough that it has been merged into the 2.6.29 version of the Linux kernel.[3] In that process, the backward-compatibility code for older formats was removed.[4] And: ]> See also ]> ]> * Cloop is a compressed loopback device module for the Linux kernel ]> * Cramfs is another read-only compressed file system ]> * e2compr provides compression for ext2 http://en.wikipedia.org/wiki/Cloop ]> The compressed loopback device or cloop is a module for the Linux kernel. It adds support for transparently decompressed, read-only block devices. It is not a compressed file system in itself. http://en.wikipedia.org/wiki/Cramfs
The compressed ROM file system (or cramfs) is a free (GPL'ed) read-only Linux file system designed for simplicity and space-efficiency. It is mainly used in embedded systems and small-footprint systems.
Unlike a compressed image of a conventional file system, a cramfs image can be used as it is i.e. without the need to decompress the image first. For this reason, some Linux distributions also use cramfs for initrd images (Debian 3.1 in particular) and installation images (SUSE Linux in particular), where there are constraints on memory and image size.
http://en.wikipedia.org/wiki/E2compr#Compression_extension ]> e2compr is a modification to the ext2 file system driver in the Linux kernel to support online compression and decompression of files on file system level without any support by user applications. ]> ]> e2compr is a small patch against the ext2 file system that allows on-the-fly compression and decompression. It compresses only regular files; the administrative data (superblock, inodes, directory files etc.) are not compressed (mainly for safety reasons). Access to compressed blocks is provided for read and write operations. The compression algorithm and cluster size is specified on a per-file basis. Directories can also be marked for compression, in which case every newly created file in the directory will be automatically compressed with the same cluster size and the same algorithm that was specified for the directory. ]> ]> e2compr is not a new file system. It is only a patch to the ext2 file system made to support the EXT2_COMPR_FL flag. It does not require you to make a new partition, and will continue to read or write existing ext2 file systems. One can consider it as simply a way for the read and write routines to access files that could have been created by a simple utility similar to gzip or compress. Compressed and uncompressed files coexist nicely on ext2 partitions. ]> ]> The latest e2compr-branch is available for current releases of 2.6 and 2.4 Linux kernels, but development is stalled. There are also older branches for older 2.0 and 2.2 kernels, which are more stable. Pity that e2compr development has stalled, I love the R/W idea (to access a mail folder many MUAs want to write to it - meaning a DVD copy does not work, has to be copied to HD first. -- Cheers / Saludos, Carlos E. R. (from 11.2 x86_64 "Emerald" GM (Elessar))