think of p2pool similar to bit torrent decentralised peer-to-peer.
p2pool that has different nodes you can connect to that make up the entire p2pool, you can either create your own node or join someone eleses, the fee paid depends on the pool you connect to.
to see the total power you can go to
http://www.blockchain.com/poolor
http://p2pool.info/I wouldn't use p2pool.info... it's got some pretty glaring mistakes (number of miners, etc). http://minefast.coincadence.com is much better.
@CryptoPanda, everyone in p2pool is mining in the same pool. There are no clusters mining separately from other clusters. It's all one, big, happy pool. You can find the total hash power of the p2pool network on any node - even the default UI. It is up to each individual node to determine any fees and donations that are charged. For example, my own node charges 0% fees (because I'm the only one who mines on it, so why bother charging myself). Windpath's node (minefast.coincadence.com that I mentioned above) also charges 0% fees.
so are all using p2pool contributing to the same total hash power or there is some federation?
I just want to make sure that my variance wont be too big if i switch to p2pool
Yes, all p2pool miners are contributing to the global p2pool rate. That rate at this very moment is 2.25PH/s. Let me ask you - how much hashing power are you planning to bring to p2pool? Variance is a bear with p2pool because of the nature of the share chain.
So the current hash power is 1-2% of the total. That would mean quite a lot of variance.