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SubjectRe: scary ext2 filesystem question
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alan@lxorguk.ukuu.org.uk (Alan Cox) said:

[...]

> Standard BSD writes metadata synchronously. This means it writes the size
> and block lists before the data. On a crash and fsck you get files that are
> correct to fsck (the block info is right) but whose data was never written.

> On Linux you may also not get the file itself if it was just created.
> fsck has to be a little smarter but there is no difference on a data
> integrity issue.

Isn't it that Linux may write data before writing metadata, so it could
write the data, but it doesn't show up in the (on-disk) file? As a result,
FFS might give you a file with garbage (allocated blocks that were never
written to), Linux might give you a short file (or loose it completely). Is
that correct?

Next question, how long are the respective windows of vulnerability to a
crash? To the next sync(2), i.e., on average 15s?

If the above is true, it looks like both are roughly equally vulnerable,
but I'd prefer the Linux failure mode.
--
Horst von Brand vonbrand@sleipnir.valparaiso.cl
Casilla 9G, Viña del Mar, Chile +56 32 672616


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