"James C. McPherson" <[EMAIL PROTECTED]> wrote:
> > If COW is such an old concept, why haven't there been many filesystems
> > that have become popular that use it? ZFS, BTRFS (I think) and maybe
> > WAFL? At least that I know of. It seems like an excellent guarantee of
> > disk commitment, yet we're all still fussing with journalled
> > filesystems, filesystems that fragment, buffer lags (or whatever you
> > might call it) etc.
> >
> > Just stirring the pot, seems like a reasonable question (perhaps one
> > to take somewhere else or start a new thread...)
>
>
> I think it was due to cpu cycles and memory not being quite
> as cheap then as they are now.
CPU cycles have not been a problem. Memory was a problem and for this reason,
I did implement virtual kernel memory for my wofs implementation.
> Oh, and that it's sufficiently different from existing ideas
> on how to write filesystems that there wasn't really any
> incentive to actually do it.
It has been implemented for SunOS-4.0
If you do not believe it, just ask Carsten Bormann ([EMAIL PROTECTED])
who did discuss the ideas with me and who did supervise my master thesis "wofs".
As a side note: I did hear around 1996 that Luftansa used WORM media to archive
important passenger data. They did not have something like wofs and did write
tar
archives only a few times per day to avoid that thousands of new small files
caused to rewrite all directroy inode data upwards to the root directory. This
verifies that other COW implementations exist before the netapps patent was
files.
Jörg
--
EMail:[EMAIL PROTECTED] (home) Jörg Schilling D-13353 Berlin
[EMAIL PROTECTED] (uni)
[EMAIL PROTECTED] (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
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