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Re: How safe is journalling?



On Oct 31, 2001  17:42 +0000, Jeremy Sanders wrote:
> The question is how safe is journalling, in general? The "ordered" mount
> option for ext3 seems pretty safe, but is it possible that if the drive's
> power went half way through writing to the journal, could it be left in an
> inconsistent state? I mean, is writing to the journal an "atomic" process?

This is the whole point of having a journaled filesystem.  The journal
is only really useful when your system fails.  Otherwise, it is just
overhead for 99% of uses.

The journal guarantees that the filesystem metadata is always consistent
after a crash.  You may lose some operations from just before the crash,
but you probably would have anyways (probably not quite as many as with
a journal), because of buffering.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/





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