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it's about the crashes!!!

Posted Mar 18, 2009 22:45 UTC (Wed) by xoddam (subscriber, #2322)
In reply to: it's about the crashes!!! by pflugstad
Parent article: Better than POSIX?

Your point is entirely correct, as far as it goes, and it validates my position.

The purpose of a journaling filesystem is *only* to ease and speed the task of recovery after an unclean shutdown. I can't emphasise this point strongly enough.

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Posted Mar 19, 2009 0:35 UTC (Thu) by butlerm (subscriber, #13312) [Link]

<em>The purpose of a journaling filesystem is *only* to ease and speed the
task of recovery after an unclean shutdown.</em>

That is not quite correct. The primary purpose of journaling in typical
journaling filesystems is to preserve metadata integrity. Filesystem
repair tools cannot repair metadata that has never been written.

The secondary purpose of journaling is to loosen ordering restrictions on
meta data updates. Assuming you want your filesystem to be there after an
unclean shutdown, that is a major advantage.

Finally, journaling filesystems are not metaphysically prohibited from
using their journals to do other useful things, such as store meta-data
undo information, for example.

it's about the crashes!!!

Posted Mar 19, 2009 5:56 UTC (Thu) by xoddam (subscriber, #2322) [Link]

Metaphysics aside, surely these primary and secondary purposes you describe themselves have the ultimate goal of saving end users the trouble of cleaning up a mess after an unclean shutdown?

it's about the crashes!!!

Posted Mar 20, 2009 21:17 UTC (Fri) by butlerm (subscriber, #13312) [Link]

Yes. The primary goal of journaling is to make the filesystem more robust
so that manual intervention after a system crash is minimized.