Messages in this thread |  | | Date | Tue, 21 Nov 2000 21:00:32 +0100 | From | Jorge Nerin <> | Subject | Re: ext2 compression: How about using the Netware principle? |
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Roy Sigurd Karlsbakk wrote: > > Hi > > With some years of practice with Novell NetWare, I've been wandering why > the (unused?) file system compression mechanism in ext2 is based on > doing realtime compression. To make compression efficient, it can't be > made this simple. Let's look at the type of volume (file system) > compression introduced with Novell NetWare 4.0 around '94: > > - A file is saved to disk > - If the file isn't touched (read or written to) within <n> days > (default 14), the file is compressed. > - If the file isn't compressed more than <n> percent (default 20), the > file is flagged "can't compress". > - All file compression is done on low traffic times (default between > 00:00 and 06:00 hours) > - The first time a file is read or written to within the <n> days > interval mentioned above, the file is addressed using realtime > compression. The second time, the file is decompressed and commited to > disk (uncompressed). > > Results: > A minimum of CPU time is wasted compressing/decompressing files. > The average server I've been out working with have an effective > compression of somewhere between 30 and 100 per cent. > > PS: This functionality was even scheduled for Win2k, but was somewhere > lost... I don't know where... > > Questions: > I'm really not a kernel hacker, but really... > - The daily (or nightly) compression job can run as a cron job. This can > be a normal user process running as root. Am I right? > - The decompress-and-perhaps-commit-decompressed-to-disk process should > be done by a kernel process within (or beside) the file system. > - The M$ folks will get even more problems braging about a less useful > product. > > Please CC: to me, as I'm not on the list > > Regards > > Roy Sigurd Karlsbakk >
Well, filesystem compresion is in NT since 4.0, in fact you can compress a file, a directory, or the whole partition, but only under NTFS. I believe that it's [un]compressed on the fly, but I'm not sure about this fact.
The [un]compression mechanism could be a kernel thread calling a userspace program (gzip, bzip2, definable) doing the actual decompresion.
Don't know, just thoughts.
-- Jorge Nerin <comandante@zaralinux.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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