> 
> Could you tell me the detail, how many master or slaver ?

1 "master" (origin) to many "slaves" (subscribers) and you can have downstream providers too (you can have slaves replicated from other slaves that are setup as providers rather than directly to the master). Slony works in replication sets, so if you had 3 servers and you'd partitioned your data into 3 sets where each server was responsible for changes to its own set you could setup replication something like

Set A on origin 1 -> subscribers 2 & 3
Set B on origin 2 -> subscribers 1 & 3
Set C on origin 3 -> subscribers 1 & 2

You really need to read the docs for yourself though:

http://slony.info/documentation/concepts.html