Introduction to MySQL INNODB engine table
InnoDB is a general-purpose storage engine that balances high reliability and high performance. In MySQL 5.6, InnoDB is the default MySQL storage engine. Unless you have configured a different default storage engine, issuing a CREATE TABLE statement without an ENGINE= clause creates an InnoDB table.
InnoDB includes all the features that were part of the InnoDB Plugin for MySQL 5.1, plus new features specific to MySQL 5.5 and higher.
Note: The mysql and INFORMATION_SCHEMA databases that implement some of the MySQL internals still use MyISAM. In particular, you cannot switch the grant tables to use InnoDB.
By default MySQL INNODB engine puts all the data for all the INNODB tables for all databases into the same file. This file will grow as it is used but will never shrink, even if you drop a very large INNODB table. This post shows how instead to have a data file per table in the database’s directory which is the same as the way the MyISAM engine works.