Re: pg_xlog safety

Vivek Khera <khera@kcilink.com> writes:
> So this leads me to my question: one of the tips for performance is to
> move the pg_xlog to its own disk.  Now that I have a spare disk I was
> considering moving pg_xlog there.  However, that's the only disk that
> wouldn't be RAID protected.  What would happen to the db if that disk
> failed?  If I were able to perform a clean shutdown,

That's a mighty big "if".  I would rather expect a failure on the WAL
drive to cause PG to shut down uncleanly (there's elog(PANIC) all
through the WAL-writing code).  Whereupon you're pretty much hosed;
you can do pg_resetxlog but you then have no idea about the consistency
of your main data area.

I think you'd be tossing away the reliability advantage of having a RAID
array at all.

            regards, tom lane