From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <06fe47922e7c54c0297b9b44b2b87c09@quintile.net> From: "Steve Simon" Date: Fri, 13 Aug 2010 17:31:23 +0100 To: 9fans@9fans.net In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Subject: Re: [9fans] information about filesystems Topicbox-Message-UUID: 476a7518-ead6-11e9-9d60-3106f5b1d025 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