MySQL 5.7 Release Notes
You can move databases or tables from the database directory to other locations and replace them with symbolic links to the new locations. You might want to do this, for example, to move a database to a file system with more free space or increase the speed of your system by spreading your tables to different disks.
For InnoDB tables, use the DATA
DIRECTORY clause of the CREATE
TABLE statement instead of symbolic links, as
explained in Section 14.6.1.2, “Creating Tables Externally”.
This new feature is a supported, cross-platform technique.
The recommended way to do this is to symlink entire database
directories to a different disk. Symlink
MyISAM tables only as a last resort.
To determine the location of your data directory, use this statement:
SHOW VARIABLES LIKE 'datadir';