First, none of the general purpose filesystems I've seen so far do data
journalling per default, since it's a huge performance penalty, even for
non-RDBMS workloads. The feature you talk about is ext3 specific (and
should be pointed out as such) and only disables write ordering, meaning
that metadata and file content updates are not synchronized.
You are right that my docs were misleading. I have improved them by
mentioning that it is _data_ flush that as part of journalling that can
be a problem, and documented that the mount option listed is
ext3-specific, not linux-specific.
Actually, I think that some of the other journalling filesystems allow
data journalling (I know ReiserFS does), they just don't default to it.
For that matter, a few (ZFS in particular) have data journalling which
can't be turned off. While it's not a tuning parameter, users should be
warned that they'll take a performance hit from it.
--Josh
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