Re: soft update vs journaling?

[Diego Calleja <diegocg@gmail.com>]

El Sun, 22 Jan 2006 04:31:44 -0500,
Theodore Ts'o <tytso@mit.edu> escribió:


> One major downside with Soft Updates that you haven't mentioned in
> your note, is that the amount of complexity it adds to the filesystem
> is tremendous; the filesystem has to keep track of a very complex
> state machinery, with knowledge of about the ordering constraints of
> each change to the filesystem and how to "back out" parts of the
> change when that becomes necessary.


And FreeBSD is implementing journaling for UFS and getting rid of 
softupdates [1]. While this not proves that softupdates is "a bad idea",
i think this proves why the added sofupdates complexity doesn't seem
to pay off in the real world. 

[1]: http://lists.freebsd.org/pipermail/freebsd-hackers/2004-December/009261.html

"4.  Journaled filesystem.  While we can debate the merits of speed and
data integrety of journalling vs. softupdates, the simple fact remains
that softupdates still requires a fsck run on recovery, and the
multi-terabyte filesystems that are possible these days make fsck a very
long and unpleasant experience, even with bg-fsck.  There was work at
some point at RPI to add journaling to UFS, but there hasn't been much
status on that in a long time.  There have also been proposals and
works-in-progress to port JFS, ReiserFS, and XFS.  Some of these efforts
are still alive, but they need to be seen through to completion"