5.4.1. Managing InnoDB Tablespaces

5.4.1.1. Enabling and Disabling File-Per-Table Mode
5.4.1.2. Specifying the Location of a Tablespace
5.4.1.3. Copying Tablespaces to Another Server (Transportable Tablespaces)
5.4.1.4. Moving the Undo Log out of the System Tablespace

Historically, all InnoDB tables and indexes were stored in the system tablespace. This monolithic approach was targeted at machines dedicated entirely to database processing, with carefully planned data growth, where any disk storage allocated to MySQL would never be needed for other purposes. InnoDB's file-per-table mode is a more flexible alternative, where you store each InnoDB table and its indexes in a separate file. Each such .ibd file represents a separate tablespace. This mode is controlled by the innodb_file_per_table configuration option, and is the default in MySQL 5.6.6 and higher.

Multiple tablespaces are useful in a number of situations:

You can reclaim disk space when truncating or dropping a table. For tables created when file-per-table mode is turned off, truncating or dropping them creates free space internally in the ibdata files. That free space can only be used for new InnoDB data.
You can store specific tables on separate storage devices, for I/O optimization, space management, or backup purposes. In previous releases, you had to move entire database directories to other drives and create symbolic links in the MySQL data directory, as described in Section 8.11.3.1, "Using Symbolic Links". In MySQL 5.6 and higher, you can specify the location of each table using the syntax CREATE TABLE ... DATA DIRECTORY = absolute_path_to_directory, as explained in Section 5.4.1.2, "Specifying the Location of a Tablespace".
You can copy individual InnoDB tables from one MySQL instance to another (known as the transportable tablespace feature).
You can enable compression for table and index data, using the compressed row format.
You can enable more efficient storage for tables with large BLOB or text columns using the dynamic row format.
You can back up or restore a single table quickly, without interrupting the use of other InnoDB tables, using the MySQL Enterprise Backup product. See Backing Up and Restoring a Single .ibd File for the procedure and restrictions.