Hallo,
http://www.postgresql.org/docs/8.2/interactive/runtime-config-wal.html

fsync (boolean)

If this parameter is on, the PostgreSQL server will try to make sure that updates are physically written to disk, by issuing fsync() system calls or various equivalent methods (see wal_sync_method). This ensures that the database cluster can recover to a consistent state after an operating system or hardware crash.

Hilft aber natürlich nicht, wenn das Dateisystem beschädigt ist.

Grüße, Christoph