Archiving to a separate database?

I’ve been using WordPress almost as long as there has _been_ a word press and as you might imagine, I have an extremely large database. I’d like to perhaps move some of my older posts to a second database, just to lighten the load. But I’d like to be able to maintain the permalink structure.

I’m sure someone must have run into this issue in the past, but oddly, searching Google hasn’t come up with the litany of articles I expected to find. I’m hoping someone here might like to share some insights into how this might be accomplished.

My first thought is that perhaps I could create a redirect in Apache for, say, anything looking in the /blog/2009 “directory,” and rewrite to another blog entirely. Does this sound right?