Oracle Exadata was pre-teased as “Extreme performance.” Some incorrect speculation shortly before the announcement focused on the possibility of OLTP without disk, which clearly would speed things up a lot. I interpret that in part as being wishful thinking.
The most compelling approach I’ve seen to that problem yet is H-Store, which however makes some radical architectural assumptions. One point I didn’t stress in my earlier posts, but which turned out to be a deal-breaker for one early tire-kicker, is that to use H-Store you have to be able to shoehorn each transaction into its own stored procedure. Depending on how intricate your logic is, that might make it hard to port an existing app to H-Store.
Even for new apps, it could get in the way of some things you might want to do, such as rule-based processing. And that could be a problem. A significant fraction of the highest-performance OLTP apps are customer-facing, and customer-facing apps are one of the biggest areas where rule-based processing comes into play.