Jeff Davis <jdavis-pgsql@empires.org> writes:
> In other words, does PostgreSQL assume that the filesystem at least
> journals the metadata?
Postgres assumes that the filesystem can take care of itself, which we
define as not losing or corrupting successfully-fsynced data. The
original BSD filesystem designs met this requirement without any
journal; they were just careful about the order in which things got
forced to disk. It appears that ext3 may not be able to meet this
requirement even with a journal :-(. But in theory a metadata journal
should be sufficient. Journaling data writes is redundant, unless maybe
the filesystem substitutes that for the ordinary idea of fsync().
regards, tom lane