Jeff,
> How all of that works WITH and/or AGAINST PostgreSQL and what metadata
> REALLY means is my bottom line quandary. Obviously that is where finding
> the warm and fuzzy place between speed and safety is found.
For your $PGDATA directory, your only need for filesystem journaling is to
prevent a painful fsck process on an unexpected power-out. You are not, as a
rule, terribly concerned with journaling the data as PostgreSQL already
provides some data recovery protection through WAL.
As a result, on my one server where I have to use Ext3 (I use Reiser on most
machines, and have never had a problem except for one disaster when upgrading
Reiser versions), the $PGDATA is mounted "noatime,data=writeback"
(BTW, I found that combining "data=writeback" with Linux LVM on RedHat 8.0
resulted in system-fatal mounting errors. Anyone else have this problem?)
Of course, if you have a machine with a $60,000 disk array and disk I/O is
unlimited, then maybe you want to enable data=journal just for the protection
against corruption of the WAL and clog files.
--
-Josh Berkus
Aglio Database Solutions
San Francisco