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Re: data recovery openoffice.sx? on ext3-partition


On Wed, Sep 04, 2002 at 09:35:50AM -0300, Alexis S. L. Carvalho wrote:
> Thus spake Stephen C. Tweedie:
> > Journalling requires the delete to be done immediately on disk for
> > various subtle reasons that I'll go into again if there's interest. :)
> I'm interested :) - though I'll understand if you just tell me to search
> the archives.

Truncate transactions (like the ones implicit in delete) can get
_really_ large.  The filesystem has bounds on the size of a
transaction, but there are essentially no bounds on the amount of
metadata a truncate can modify.  So to fit things into the limited
space in the journal, ext3 needs to be able to split a truncate over
multiple transactions.

And that is not possible unless we record, on disk, the incremental
progress of each bit of the truncate.  If we didn't record progress,
then if we crashed in the middle of the truncate, the metadata on disk
would be in a mess, and ext3 is supposed to prevent that!

But a side-effect of keeping the on-disk progress of the truncate
coherent is that once the truncate completes, all record of the
original data has been wiped out.


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