Archiving old email?

[Patrick Goetz]

I have some users whose mail folders are approaching 2GB in size. 
Unfortunately they can't delete any of this mail, but that doesn't mean 
that it needs to be lugged around, indexed, and copied to local mail 
caches as part of a live mail system.  I find that the probability of 
needing to look at mail more than 5 years old is roughly 0%/year.

I was going to ask if anyone had any ideas about archiving old mail, but 
then noticed that cyrus 3.0 is going to support some kind of archiving 
system:

   Archive support has arrived! Requires addition of an archive 
partition. (See archive_* options in imapd.conf)

Can anyone elaborate on what this actually means?