Migrating MySQL Directory

Once I created a raid, mounted it as a disk system partition and transferred the MySQL directory directly to it, but in this case there were drawbacks, the lost+found directory could appear, it could not be used for other data, etc., after that I began to transfer the MySQL directory not directly to the partition, but created a directory on it and transferred it to it.

See my article:
Moving the MySQL data directory to a new location

Suppose you created a raid and mounted it in the /srv/raid10/ directory, at the time of this writing, I created a level 10 raid from 10 SSDs for a highly loaded database.
Create a directory for MySQL data:

mkdir /srv/raid10/mysql/

Let’s specify the user and group on behalf of which the MySQL server is running:

chown mysql:mysql /srv/raid10/mysql/ -R
chmod 755 /srv/raid10/mysql

You can also do this:

chown --reference=/var/lib/mysql /srv/raid10/mysql
chmod --reference=/var/lib/mysql /srv/raid10/mysql

Let’s open the MySQL server configuration file in a text editor, for example:

nano /etc/mysql/mysql.conf.d/mysqld.cnf

Let’s change the path to the files to a new location:

[mysqld]
datadir=/srv/raid10/mysql

I also specified in the /etc/mysql/mysql.conf.d/mysqld_safe_syslog.cnf file:

[mysqld_safe]
datadir=/srv/raid10/mysql

If apparmor is used, then in its configuration it is also necessary to specify a new directory, open the apparmor configuration, for example:

nano /etc/apparmor.d/usr.sbin.mysqld

I found lines:

# Allow data dir access
  /var/lib/mysql/ r,
  /var/lib/mysql/** rwk,

And I added after them:

  /srv/raid10/mysql/ r,
  /srv/raid10/mysql/** rwk,

To apply the changes, restart apparmor:

/etc/init.d/apparmor reload
systemctl restart apparmor

Now you can stop the MySQL server:

systemctl stop mysql

We copy the data to a new location:

rsync -av /var/lib/mysql /srv/raid10/mysql

We check:

ls -l /srv/raid10/mysql/

We start the MySQL server:

systemctl start mysql
systemctl status mysql

Let’s reboot the server to make sure that the raid array was mounted at system startup and the MySQL server starts successfully:

reboot