Does the Disk Usage in cPanel (Disk Used in WHM) include MySQL usage?
By default, MySQL usage is included in the Disk Usage/Disk Used calculation. However, MySQL usage is not restricted by the account quota. This is because MySQL has no concept of database ownership built-in, and all of the files it uses are owned by the 'mysql' user, not the cPanel user. So a cPanel user that has exceeded their disk quota will not be able to perform actions in cPanel that would cause the disk usage to grow, but they could still perform actions on their databases that would cause the database sizes to increase.