[Update] - D'oh! I meant What LJ cluster are you on? =P Sorry... akiki, diannadinoble, bellajellybean, go change your answer here =D =D Although, I think I can guess... akiki = Chef; diannadinoble = Cartman; bellajellybean = Santa(?)
I'm on Chef. I'm just curious to see where people are. I'm not sure how to find someone else's cluster without asking... And I haven't done a poll in a long time.
Each cluster is a combination of hardware(?), software, web server, database, master, slaves, etc. It was done to make rendering the FRIENDS view more efficient because pulling up a Friends page was the most resource intensive request.
The way it's designed, everyone is assigned a cluster. Lookups within your own cluster would be super fast, lookups across clusters would be a little slower. At best, all your friends are in the same cluster. At worst, none of your friends are in the same cluster as you (which is not very likely and I'm trying to think if that's even possible).
The cluster criteria (how to decide who to put in what cluster) was geographical region (approximately, I think)... I don't know if that's changed. Their reasoning was your LJ Friends are more likely to be in your own region (ie. RL friends). I told them I disagreed with this, that the whole purpose I'm online is specifically to meet people from all over the world - people that I would never have had the chance to talk to otherwise. Why would I go online to only stay in touch with people I can phone or see in person? But I guess I come from a different net.era where internet was for "long distance contact for the price of a local phone call".
I'm pretty sure my friends are all over North America with some overseas, so I expect all kinds of different clusters to show up in the poll. If most of your friends live near you, you'll probably all be in the same cluster.