Re: soft update vs journaling?

[John Richard Moser <nigelenki@comcast.net>]

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Diego Calleja wrote:
> 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. 
> 

Yeah, the huge TB fsck thing became a problem.  I wonder still if it'd
be useful for small vfat file systems (floppies, usb drives); nobody has
led me to believe it's definitely feasible to not corrupt meta-data in
this way.

I guess journaling is looking a lot better. :)

> [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"
> 

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