Joseph Shraibman <jks@selectacast.net> writes:
> If I put the pg_xlog directory on its own disk, then that disk fails,
> does that mean the postgres is hosed or does it just mean that postgres
> no longer safe from a power outage?
The latter. The WAL is actually write-only during normal operation.
However you need to define "fail". If it fails in such a way that the
OS notices (which is likely) then the database is going to lock up
because it can't write to WAL.
regards, tom lane