Monitoring Service impact?

Openfire 3.5.2, Red Hat Enterprise 5, Active Directory, MySQL, Monitoring Service - 1.0.1

Hi all, just after a bit of advice on the Monitoring Service / Message Archiving functionality. Our dept head wants archiving of conversations switched on - and before I press the button I’d like to know a little about likely performance overhead and importantly the likely impact on disk space. Of course this is very much a “how long is a piece of string” question - but some real world examples would be very useful. Openfire is running on a VM with 2GB RAM (Java memory in OF increased to 1GB), and a 60GB data volume - currently only 5% in use. Usage via Spark is currently fairly low - less than 100 users and it’s certainly not being hammered, but this is increasing day by day as we roll out the service to other areas.

Any pointers / advice appreciated.