I'm not a PostgreSQL expert, but I was reading around for your same reasons, and found some info here: http://www.postgresql.org/docs/9.4/inte ... ackup.html
Looking at the three options, first of all file system level backup is not an option since it can only be done with the database in shutdown state. PG Dump seems to be a good solution, and looking at the commands seems it can be easily integrated with a pre-job script. This obsiously have the limit to restore the entire database at the same state of the time of the dump itself, but I think being it the database for vCenter, is good enough.
There's another option to do point-in-time backups which sounds similar to Oracle archive logs, but I don't honestly see the need to do so for the vCenter database, is more suited for other production uses of PostgreSQL.