Check manual page of mysql_capacity
Size of MySQL tablespaces
This check verifies the space used by MySQL databases as
returned from MySQL. The information is built by summing up
the space for indices and tables of a given database.
It relies on the information returned from MySQL, which can be incorrect
as MySQL does not always account for all database information.
In practice, the check works well for InnoDB.
This should even include InnoDB on raw partitions.
MyISAM reporting is not possible as MySQL does not make the
data available. (See the dirsize checks as a workaround should you
really use MyISAM)
The check will go to WARN or CRIT levels if a user-specified
limit is exceeded.
The check generates one item per Database found.
Internal MySQL databases are ignored.