Heatmap Tracking Requires
- PHP 5.4 or better
- PHP cURL library installed
- PHP MySQLi library installed
- MySQL database
Around 15MB - 20MB of disk space
While it's impossible to really give you an accurate number as it really depends on how interactive your users are, and how many visitors you receive, in general database storage space required is pretty small, unless you're servicing 1000's of visitors who click and scroll and visit 10's of pages each day.
In a test we did, 10,000 sessions recorded on a mini-site of about 10 pages only used about 100mb of space.
We also do provide a data management area within each project which allows you to see just how much DB space each project uses, and you're also able to purge the database for a specific project if need be. I hope that helps you gauge a bit better.