I have a MYSQL database on my SDA. It's mostly all one schema with "popular" tables in it. I want to store the less "popular" tables of the schema (which take up another 1TB or so) on my SDB partition.
What is the right way to do this? Do I need another MYSQL server running on that drive? Or can I simply set like DATA_DIRECTORY= or something? This is Ubuntu and MYSQL 5.7.38. Thank you for any help, it's much appreciated.
As of MySQL 8.0.21, the ability to specify the data directory per table has finally improved.
CREATE TABLE t1 (c1 INT PRIMARY KEY) DATA DIRECTORY = '/external/directory';
Read https://dev.mysql.com/doc/refman/8.0/en/innodb-create-table-external.html#innodb-create-table-external-data-directory for details.
In earlier versions of MySQL, you could use symbolic links. That is, the link still has to reside under the default data directory, but the link can point to a file on another physical device.
It was unreliable to use symbolic links for individual tables in this way, because OPTIMIZE TABLE or many forms of ALTER TABLE would recreate the file without the symbolic link, effectively moving it back to the primary storage device. To solve this, it was recommended to use a symbolic link for the schema subdirectory instead of individual tables.
To be honest, I've never found a case where I needed to use either of these techniques. Just keep it simple: one data directory on one filesystem, and don't put the data directory on the same device as the root filesystem. Make sure the data storage volume is large enough for all your data. Use software RAID if you need to use multiple devices to make one larger filesystem.