Nick,
> ...About one year ago I considered moving to a journaling file system, but
> opted not to because it seems like that's what WAL does for us already. How
> does putting a journaling file system under it add more reliability?
It lets you restart your server quickly after an unexpected power-out. Ext2
is notoriously bad about this.
Also, WAL cannot necessarily recover properly if the underlying filesystem is
corrupted.
> I also guessed that a journaling file system would add overhead because now
> a write to the WAL file could itself be deferred and logged elsewhere.
You are correct.
--
-Josh Berkus
Aglio Database Solutions
San Francisco