The InnoDB Plugin for MySQL contains several important new features:

Note that the ability to use data compression and the new row format require the use of a new InnoDB file format called “Barracuda”. The previous file format, used by the built-in InnoDB in MySQL versions 5.0 and 5.1 is now called “Antelope” and does not support these features, but does support the other features introduced with the InnoDB Plugin.

The InnoDB Plugin is upward compatible from standard InnoDB as built in to, and distributed with, MySQL. Existing databases can be used with the InnoDB Plugin for MySQL. As described in Section 9.5, “Configuring the InnoDB Plugin”, the new parameter innodb_file_format can help protect upward and downward compatibility between InnoDB versions and database files, allowing users to enable or disable use of new features that can only be used with certain versions of InnoDB.

The built-in InnoDB in MySQL since version 5.0.21 has a safety feature that prevents it from opening tables that are in an unknown format. However, as noted in Section 11.2, “The Built-in InnoDB, the Plugin and File Formats”, the system tablespace may contain references to new-format tables that will confuse the built-in InnoDB in MySQL. These references will be cleared in a “slow” shutdown of the InnoDB Plugin.

With previous versions of InnoDB, no error would be returned until you try to access a table that is in a format “too new” for the software. Beginning with version 1.0.1 of the InnoDB Plugin, however, to provide early feedback, InnoDB will check the system tablespace to ensure that the file format used in the database is enabled for use before it will start. See Section 4.4.1, “Startup File Format Compatibility Checking” for the details.