kfs is a simple, non-backed up filesystem designed for stand alone machines
kenfs is the older main file server, it runs stand alone on a single machine
and can use either magnetic disks or WORM disks and provides access to previous
backups online. it supports a narrower range of hardware than the maion kernel
but has its fans due to its simplicity and reliability.
cwfs is n implemention of kenfs as a user program for plan9, it can read and
write kenfs
filesystems and can be used as the main filesystem for a system to boot from
(and then serve).
fossil is a write buffer which acts as a file system and can be used to replace
kfs
on simple machines (laptops), it can take regular temporary snapshots of the
system state and
present them as backups (e.g. every 15 mins), though sadly this part of the
code seems to be
broken.
Most often fossil is used in conjunction with venti which provides permenant
online backups. venti works a bit like the back end of kenfs except that it adds
a network interface (so other apps and OSs can access venti) and it does
compression
before storing blocks.
both kenfs and venti strip duplicate blocks so as to reduce the size of their
backups,
venti detects duplicates using an sha1 checksum so copying files on a venti
backed
has almost no overhead (i.e. only the directory entries).
I run two combined file/cpu/auth servers with fossil and venti on both, others
run
kenfs on a dedicated machine and still others run cwfs on a file/cpu/auth
server.
its a complex debate and I'am sure others will have opinions.
see here for some more info:
kenfs:
http://plan9.bell-labs.com/sys/doc/fs/fs.pdf
http://plan9.bell-labs.com/who/seanq/cw.pdf
http://plan9.bell-labs.com/magic/man2html/4/fs
venti
http://plan9.bell-labs.com/sys/doc/venti/venti.pdf
http://plan9.bell-labs.com/magic/man2html/8/venti
fossil:
http://plan9.bell-labs.com/sys/doc/fossil.pdf
http://plan9.bell-labs.com/magic/man2html/4/fossil
cwfs:
http://plan9.bell-labs.com/magic/man2html/4/cwfs
kfs:
http://plan9.bell-labs.com/magic/man2html/4/kfs
-Steve
