Recently seen in ACM Operating Systems Review (this is the first time I've found as many as 1 interesting article in it in a while, and there were 3 things I found worthwhile...):
NTT (of the recent "NTT Power Hour") have created a new filesystem: <http://www.nilfs.org/en/> NILFS is a log-structured file system developed for Linux. In effect, it provides the "moral equivalent" to MVCC for filesystems; overwrites are equivalent to delete/insert, and requires a "Cleaner" process in order to clean out formerly-used space. It ought to have two merits over journalling filesystems: 1. It doesn't need to write data twice, which should improve performance 2. It doesn't need to repetitively overwrite metadata, which should improve crash safety. On the latter, per the paper: "... These journaling filesystems enable fast and consistent recovery of the file system after unexpected system freezes or power failures. However, they still allow the fatal destruction of the file system due to the characteristic that recovery is realized by overwriting meta data with their copies saved in a journal file. This recovery is guaranteed to work properly only if the write order of the on-disk data blocks and meta data blocks is physically conserved on the disk platters. Unfortunately, this constraint is often violated by the write optimizations performed by the block I/O subsystem and disk controllers." It's still at a somewhat early stage, as they haven't completed coding the Cleaner. (Probably should call it the Reaper... :-)) By the way, the Google SOC 2005 also produced one: <http://logfs.sourceforge.net/> NetBSD used to have a LFS; has that gone anywhere? Or been essentially dropped? -- let name="cbbrowne" and tld="cbbrowne.com" in String.concat "@" [name;tld];; http://linuxdatabases.info/info/emacs.html "I develop for Linux for a living, I used to develop for DOS. Going from DOS to Linux is like trading a glider for an F117." -- <[EMAIL PROTECTED]> Lawrence Foard ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
