Backup and restore

I will be installing moodle soon on a new account and I'm concerned about how quickly the uploaded documents will eat up the alotted disk space on our hosting account.
What I would like to do is keep the discussion / classroom threads permanently online for archival purposes even after the class has ended so students can log in and check their previous work if they like. I also want to keep a permanent record of all the word docs that have been uploaded, but keep that record on an offline server (with no disk space contrainsts). So ideally three months after the class has ended all the uploaded docs will be removed from the online server and transferred to the offline server. How would I go about doing this? Will this break the links that are on the classroom boards or is there a built in feature to do this? (If the student tries to access an archived word doc I will create a custom error page that notifies them that their file has been archived and that they should contact the admin to obtain a copy).
Hopefully this all makes sense. I appreciate any help you can offer, this is a very important issue for us.
Thank you!

Nurhan