Because the InnoDB Plugin introduces a new file format, with new on-disk data structures within both the database and log files, there are important restrictions on the use of the plugin in typical user environments. Specifically, you should pay special attention to the information presented here about file format compatibility with respect to the following scenarios:

WARNING: Once you use the InnoDB Plugin on a set of database files, take care to avoid crashes and corruptions when using those files with an earlier version of InnoDB, as might happen by opening the database with MySQL when the plugin is not installed. It is strongly recommended that you use a “slow shutdown” (SET GLOBAL innodb_fast_shutdown=0) when stopping the MySQL server when the InnoDB Plugin is enabled. This will ensure log files and other system information written by the plugin will not cause problems when using a prior version of InnoDB. See Section 11.3, “How to Downgrade”.

Because of these considerations, and although it may be useful in certain circumstances to use the plugin in a temporary way as just described, many users will find it preferable to test their application with the plugin and use it on an on-going basis, without reverting back to the standard, built-in InnoDB.

WARNING: If you dump a database containing compressed tables with mysqldump, the dump file may contain CREATE TABLE commands that attempt to create compressed tables, or those using ROW_FORMAT=DYNAMIC in the new database. Therefore, you should be sure the new database is running the InnoDB Plugin, with the proper settings for innodb_file_format and innodb_file_per_table, if you want to have the tables re-created as they exist in the original database. Typically, however, when the mysqldump file is loaded, MySQL and InnoDB will ignore CREATE TABLE options they do not recognize, and the table(s) will be created in a format used by the running server.

WARNING: If you use MySQL replication, you should be careful to ensure all slaves are configured with the InnoDB Plugin, with the same settings for innodb_file_format and innodb_file_per_table. If you do not do so, and you create tables that require the new “Barracuda” file format, replication errors may occur. If a slave MySQL server is running the built-in InnoDB, it will ignore the CREATE TABLE options to create a compressed table or one with ROW_FORMAT=DYNAMIC, and create the table uncompressed, with ROW_FORMAT=COMPACT.

WARNING: The current version of InnoDB Hot Backup does not support the new “Barracuda” file format. Using InnoDB Hot Backup Version 3 to backup databases in this format will cause unpredictable behavior. A future version of InnoDB Hot Backup will support databases used with the InnoDB Plugin. As an alternative, you may back up such databases with mysqldump.