question about Postgresql and rsync

Hi,
Does anyone know if it would be safe to use rsync to mirror a Postgresql
setup to a backup server?

I need to create a exact duplicate for a disaster recovery server, the
disaster recovery server would not be in use until the production one
went down for
some reason.

It seems to me that if the postmaster is stopped it should be safe.
Comments?

Thanks,

Tony Caduto