Rsync'ed postgres databases won't allow log-on, gets "cache lookup failed for relation" error
Make sure that postgres is killed on the side you are rsyncing from as well as the side you rsynced to (you goofus).

Smart Peter: After you ran rsync what files did it copy?
Goofus Peter: Um almost everything, except the network stuff, I needed that
Smart Peter: so,  everything like all the pid's and cron and everything
Goofus Peter:  I guess so, but postgres was off on the machine I was copying from
Smart Peter: Well, was postgres on on the machine you were copying too?
Goofus Peter: Oh crap

... Later ...

Goofus Peter: Hey, it still didn't work, and now I can't even start postgres!
Smart Peter: Is it running
Goofus Peter: How could it be running if I couldn't even start it?
Smart Peter: Because it was running all along!
Goofus Peter: (gets cut off)
Smart Peter: Because you have a cron job that restarts it
Goofus Peter: But I killed cron
Smart Peter: Did you kill it, or did you stop the service
Goofus Peter: Stopped the service...
Smart Peter: So basically, you left the bodies and moved the headstones?
Goofus Peter:  OK I'll make sure everything is dead and call you back

... Time passes ...

Goofus Peter: OK everything worked
Smart Peter: Great, I'll go tell stackexchange!