I did a simple archive forum. Transferred 150 000 posts there. Left only 2000 posts on the main board.
I used the bulk move plugin, with some hack (displaying 2000 threads at once instead of 30). I suggest this routine should not have "hard wired" number of posts but a variable that can be changed easily. After the big 20 000 thread move I reduced the bulk move display to 200 threads
Results were amazing. CPU load went down a lot. Data base query time for a page went down from 2 seconds to 0.2 seconds.
This might be a bit board specific. This board is mainly a gossip board. So people don't dig into the past, they mainly comment on last 1-5 day's posts.
Thank god, not much searching is going on there either.
I still would like my prior suggestions implemented:
a) restrictable search rights. Search is actually scary if ever it gets abused.
b) indexing by posting day or posting week, thus allowing to just blank out all posts older than 2 days, increasing database speed without the database artifact
