Running with fsync=off

[Benjamin Arai <barai@xxxxxxxxxx>]

I want to be able to do large updates on an existing backed up database 
with fsync=off but at the end of the updates how do I ensure that the 
data gets synced?

Somebody said running "sync ; sync; sync" from the console.  This seems 
reasonable but why not just "sync" or is there another command I should 
ruyn after the update either in postgres or the console?