Re: turning fsync off for WAL

Ahh. I think you can use this effectively but not the way you're describing.

Instead of writing the wal directly to persistentFS what I think you're better
off doing is treating persistentFS as your backup storage. Use "Archiving" as
described here to archive the WAL files to persistentFS:

http://postgresql.com.cn/docs/8.3/static/runtime-config-wal.html#GUC-ARCHIVE-MODE