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SubjectRe: precise characterization of ext3 atomicity
Hans Reiser <reiser@namesys.com> wrote:
>
> Perhaps the following is correct?
>
> By contrast, ext3 in data=journal and data=ordered modes only guarantees the atomicity of a single write
> that does not span a page boundary, and it guarantees that its internal
> metadata will not be corrupted even if your application's data is
> corrupted after the crash (due to the application spreading what should be committed atomically across more than one block).

Correct != comprehensible ;)

"In all journalling modes ext3 guarantees metadata consistency after a
crash. In its data=journal and data=ordered modes ext3 also guarantees that
user data is consistent with metadata after a crash.

However ext3 does not provide user data atomicity guarantees beyond the
scope of a single filesystem disk block (usually 4 kilobytes). If a
single write() spans two disk blocks it is possible that a crash partway
through the write will result in only one of those blocks appearing in the
file after recovery"

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