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I think the NCR Teradata approach is one of the most interesting. It is made up of a number of nodes (each quad Intel processor systems with separate memory and disk), each broken down into a number of logical machines. Data is hashed across all the nodes in the systems based on the data's indexing. So if two tables have the same indexing the join takes place at the "logical machine" level, and then the result is spooled together. The largest systems approach 300 nodes, with over 2,000 logical machines and 150 Tb of disk (some used to duplicate tables in case of node failure).
Personally, it has it's drawbacks, but if the indexing is right, you can join hundred million row tables at amazing speed. Based on my experience in data warehousing, it's performance Oracle can't touch (no, I'm not paid by NCR...just a user).