Coordination of mining pools

[Geir]

I know the answer is out there but I can’t find it.
As I understand it, when you do mining you send a getwork(), get data back and do a sha256(sha256()) of the first 80 bytes (of the data part). If it’s not below the target you increase the nonce and try again. Everyone is not working on the same thing since merkle root is different for everyone.

My question is for mining pools, I guess everyone gets the same data from GetWrok(). How is it then coordinated so that they all don’t just tests the same hashes??

[Geir]

Ok i found the answer, for you who are interested:
The pool sends a different header to every miner, then the miner goes trough the nonce.

OK so next question:
I've looked at the data returned from the miner to the pool. Looks like its the header again with the nonce that worked (the golden one), but also the merkle root changes. What is this all about???