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SubjectIs ReiserFS really a journaling file system, or is it really just a synchronous-metadata file system like BSD FFS?

I have seen the ReiserFS described as a "journaling filesystem", but
in examining the project web page, it appears not to be. In fact, I
see described there a "journaling patch" which seems to journal FS
metadata, but not file contents. In particular:

This is metadata logging only. If you hit the reset button in the
middle of a kernel compile, you will end up with a bunch of
invalid .o files, but the directory tree will remain valid. If
you run sync a few times and then hit the reset button, data and
metadata will both be valid.

As I understand it, a journaling file system is one in which, if you
pull the plug at any point, all the metadata _and_ file data accurately
reflect a recoverable self-consistent state at a some instant. IIUC,
it is what is promised by Veritas and the IBM and SGI systems which are
being groomed for inclusion. Not to journal file contents somewhere
seems to make such semantics impossible.

Is it that the file system layout itself supports journaling, but
that the VFS layer doesn't support the semantics needed really to
get it?

(This also begs the question, if terminology is so abused here, is ext3
really a journaling fs? (And, is ext2 a "journaling fs" just because
the ext3 patch exists?))

I hope my impression is wrong, and that in fact all these file systems
provide similar recovery semantics. Can someone answer authoritatively?

Nathan Myers

p.s. I know ReiserFS has all kinds of cool semantics in addition to
traditional file-system stuff; I'm just asking about its recovery

p.p.s. Sorry about the title, it was my impression that all
ReiserFS-related postings have to have long titles. :-)

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