I don't know, but the original FreeBSD responder may have meant
LFS, the log-structured filesystem, which the BSDs have
recently revamped. It is a true journaling file system distinct
from FFS/UFS, and not merely soft-updates on top of a
traditional block-structured file system. With LFS, you always
append on writes, rather than overwrite. Thus, writes are
fast, and if the machine crashes, since the previous data has
not been overwritten, you can recover quite quickly. Of
course, with finite disks you need to do some
garbage-collecting, but LFS does all of that for you, and also
has some optimizations so that reads are still fast.
Cool concepts, since it is solving a different problem, like fast
transaction support, than traditional filesystems. There are a
bunch of filesystem papers on LFS by John Ousterhout, Margo
Seltzer, Keith Bostic, and Kirk McKusick that provide more
details -- look at the mount_lfs man page on any recent *BSD
system for the exact references.
Brian Grayson (a NetBSD fan in his spare time)
(Not speaking for Motorola, of course!)
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