How do you upgrade for production servers?

[Arnau <arnaulist(at)andromeiberica(dot)com>]

Hi all,

  This is a general question about which procedure you follow when you 
upgrade your productions servers. Let's say we have a server running and 
older version and I want to install the latest version on the same 
server. Do you install slony? do you dump all the databases, install the 
latest version and after you restore? any other procedure? I'd like to 
have my production server down as less time as possible.


Thank you very much and have a great new year :D
--
Arnau