by Mark on Tue Apr 08, 2008 9:26 am
It's generally not the file space you have to worry about, which can vary from 2MB's to 20MB's (nothing by modern standards). The issue is usually how big the database gets, though most modern forum software will use a single table for all the main post data and search it using 'fulltext', this saves the search index having to make its own duplicate, thus reducing space.
Judging how much space a forum is likely to use can be very difficult and generally I wouldn’t worry about it unless your site receives thousands of new posts each day. It would take thousands of posts just to use up 1 to 2MB’s or so since MySQL is quite good at saving space.