Messages in this thread | | | Date | Thu, 4 Sep 2003 18:05:16 +0200 | From | Antonio Vargas <> | Subject | Re: precise characterization of ext3 atomicity |
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On Thu, Sep 04, 2003 at 11:15:40AM -0700, Mike Fedyk wrote: > On Thu, Sep 04, 2003 at 08:25:18PM +0400, Hans Reiser wrote: > > In data=journal and data=ordered modes ext3 also guarantees that the > > metadata will be committed atomically with the data they point to. 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. > > And how does reiser4 do this without changing the userspace apps?
It won't.
[ snip ] > Most files are written with several write() calls, so even if each call is > atomic, your entire file will not be there. > > Also, ext3 could claim the same atomicity if it only updated meta-data on > write() call boundaries, instead of block boundaries.
There will be a new API to support userspace-controlled multifile transactions.
At first stab, multifile transactions will be used internally to implement extended attributes.
Now, another question is.. will the transaction API support commit() and rollback()? *grin*
(wonder about coding a simple transactional database with shell scripts ;)
-- winden/network
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