Question

In my MySQL installation I have one InnoDB database that I know will grow very large so I have decided to move it to its own disk. I was hoping to do this by moving the files to the other disk and then create a symlink but I run into errors!

This is what I have done:

1) In my.cnf I have set

[mysqld]
innodb_file_per_table

(This works, I have one .ibd per .frm in the database folder.)

2)I have checked if symlinks are ok with SHOW VARIABLES LIKE "have_symlink";

(I know that the documentation says:

Symlinks are fully supported only for
MyISAM tables. For files used by
tables for other storage engines, you
may get strange problems if you try to
use symbolic links.

But I need foreign keys…)

3) I moved the database folder and created a symlink.

4) Restarted mysql and tried:

 mysql> USE db_name
 Database changed
 mysql> SHOW TABLES;
 ERROR 1018 (HY000): Can't read dir of './db_name/' (errno: 13)
 mysql> exit
 user@comp# perror 13
 OS error code  13:  Permission denied

symlink is (as expected) lrwxrwxrwx mysql mysql db_name -> /path-to/db_name/

database folder permissions are drwx------ mysql mysql

all file permissions are -rw-rw---- mysql mysql

I am using Ubuntu 10.04 Server with MySQL 5.1.41 (default from apt).

Have any of you done this successfully?

Answer 1

I’m not sure your solution is the best idea. See my post here:

http://www.mysqlperformanceblog.com/2010/12/25/spreading-ibd-files-across-multiple-disks-the-optimization-that-isnt/

There is also this other thread here:

Innodb; multiple data directories