I wrote some code for DB load balancing back in January, but we haven't had a slave server to test it on until now. I'm happy to announce that it's now running.
Ariel is being used as a slow query server. Currently, it is handling watchlist queries and miser mode queries (although only with the magic parameter). Selecting which queries to send to Ariel is currently ad-hoc, but something more permanent should find its way into CVS in the next week or two.
The obvious application for this is enabling full-text search. However we still need to rebuild the searchindex table.
-- Tim Starling