如何在InnoDB表的已安装分区上更改数据目录？

Question

I'm using MariaDB 5.5.44. I want to create InnoDB table which store data across mounted partition.

Consider I had mounted partition /var/log/storage as follow:

/dev/sda2       6.5G  3.6G  2.6G  59% /
/dev/sda1       395M   32M  338M   9% /boot
/dev/sda6       5.3G   22M  5.0G   1% /var/log/storage

To create table I use following query:

create table InnoDB_Test(a INT) DATA DIRECTORY='/var/log/storage/MySQL' INDEX DIRECTORY='/var/log/storage/MySQL' engine=InnoDB;

But it store data in /var/lib/mysql instead of /var/log/storage/MySQL

Same If I tried with MyISAM using following query & which works as expected:

create table MyISAM_Test(a INT) DATA DIRECTORY='/var/log/storage/MySQL' INDEX DIRECTORY='/var/log/storage/MySQL' engine=MyISAM;

How I can change data directory to mounted partition in InnoDB? Why data partition works in MyISAM & not in InnoDB?

Thank you in advance.

Answer 1

I wanted to do this (for partitioning) but the mysql documentation says "No".

Here's the relevant section from this page: https://dev.mysql.com/doc/refman/5.5/en/partitioning-overview.html

19.1 Overview of Partitioning in MySQL

The DATA DIRECTORY and INDEX DIRECTORY options have no effect when defining partitions for tables using the InnoDB storage engine.

So it'll work if your storage engine is using MyISAM.

Your options are to:

1. globally specficy the data directory in mysql command line options or my.cnf file to point to /var/log/storage. eg --datadir=/var/log/storage
2. move the whole mysql data dir to /dev/sda6 and mount it to /var/lib/mysql. This is pretty much the same as the first option, except you get to keep the path /var/lib/mysql
3. create a tablespace directory for your innodb data and mounting /dev/sda6 to it.

For the third option, to put innodb data in a seperate directory you configure innodb to create a file per table

# my.cnf
[mysqld]
innodb_file_per_table=1

Once you've rebuilt your db/tables you'll find that a directory (eg /var/lib/mysql/mydb) for your tablespace will get created with individual files for each table.

Then you can copy the tablespace directory and files over to sda6 and mount /dev/sda6 to /var/lib/mysql/mydb

Apparently mysql server 5.6 doesn't suffer this limitation.