How to not run out of MySQL disk space
A very useful tool to monitor to avoid running out of disk space is "PA Server Monitor Ultra". It can be setup to alert you over email when the disk space is low.
As a first action when you are at risk of running out of disk space read "How to not run out of disk space"
Make sure you delete log files, and disable IIS logging. And if appropriate enable GpsGate Cleanup to delete old data from the database. All described in the guide linked to above.
Another option to using Cleanup is to extend the MySQL database over multiple disks. Add a new disk and use this guide to extend the database to the new disk
For larger servers use high performance SSD disks!
How to optimize your GpsGate Server performance and user experience!