[Zope] load balancing between multiple zope instances, readonly mode.

I'm putting together a zope site that stores all non-static data in a backend database (it's really just a fancy way to edit the database). I'm concerned about hangs and delays in the database queries, so what I'm proposing to do is to run multiple zope instances with the same database, and a load balancer in front of them. so, the magic question: can I run multiple zopes off the same var/ directory, with all but one in readonly mode? I thought I remembered seeing something about readonly mode in the mailing list, but I can't find it now... and can anyone think of other ways to do this, without creating fresh copies of the entire tree each time? thanks, Anthony