Ever growing mailboxes and archiving

[Paolo Cravero]

Good morning.
I am looking for a server-side archiving solution to be applied to a 
relatively large cyrus installation.

The customer eats up ca 4 TB of data over about 4000 accounts. No quota.

The competition is: who will die first? The web-based client or our 
SAN+backup system? :-)

I am aware cyrus can handle the folder tree of a single account over 
different cyrus partitions. This might mean more complex maintenance and 
way longer restore times but it does indeed require 100% good user 
behavior in archiving old messages in the proper subtree. Unless 
administratively old messages are moved away once a year (what an impact 
on I/O and backups...).

A good search engine did not return useful links, or I used wrong keywords.

Some commercial email products have solutions to handle old messages or 
just their attachments: is there something that would apply to our 
beloved cyrus?

How do you handle large and rarely accessed old messages?

Thanks,
Paolo

PS: I am not after a regulations compliant archiving, just something to 
offload the main (expensive) storage.