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We using 3 freshly deployed VMs running a minimal install of CentOS 7 x86_64

• Cluster node 1 has hostname HOST_G and IP address IP_HOST_G
• Cluster node 2 has hostname HOST_L and IP address IP_HOST_L
• Cluster node 3 has hostname HOST_F and IP address IP_HOST_F

The cluster is reachable throught the load balancer miracle.lnf.infn.it with ip address 193.206.84.215.

Create a mariadb repository /etc/yum.repos.d/mariadb.repo using following command:

# cat > /etc/yum.repos.d/mariadb.repo

Insert the following directives:

# MariaDB 10.1 CentOS repository list - created 2015-10-14 13:45 UTC
# http://mariadb.org/mariadb/repositories/
[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.1/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

terminate by the [Enter] key. To save and exit press [CTRL]+[d] keys.

Install the MariaDB Galera Cluster by executing the following command on all nodes:

# yum install MariaDB-server MariaDB-client rsync galera

Start the mariadb service and enables the service to be started on boot:

# systemctl start mariadb
# systemctl enable mariadb

Run the mysql_secure_installation script so we can improve the security. Run the following command on all nodes:

# /usr/bin/mysql_secure_installation

we don’t set the root password and we accept all defaults.

Now, we create the database user. The sst_user is the user which a database node will use for authenticating to another database node in the State Transfer Snapshot (SST) phase.

On the HOST_G node run the following command:

# mysql
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_L>' IDENTIFIED BY [PASSWORD];
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_F>' IDENTIFIED BY [PASSWORD];
mysql> GRANT ALL PRIVILEGES on *.* to sst_user;
mysql> FLUSH PRIVILEGES;
mysql> quit

On the HOST_L node run the following command:

# mysql
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_G>' IDENTIFIED BY [PASSWORD];
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_F>' IDENTIFIED BY [PASSWORD];
mysql> GRANT ALL PRIVILEGES on *.* to sst_user;
mysql> FLUSH PRIVILEGES;
mysql> quit

Finally, on the HOST_F node run the following command:

# mysql
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_G>' IDENTIFIED BY [PASSWORD];
mysql> GRANT USAGE ON *.* to sst_user@'<IP_HOST_L>' IDENTIFIED BY [PASSWORD];
mysql> GRANT ALL PRIVILEGES on *.* to sst_user;
mysql> FLUSH PRIVILEGES;
mysql> quit

First stop the mariadb services on all nodes:

# systemctl stop mariadb

Next, We are going to create the MariaDB Galera Cluster configuration by the following command on all nodes:

# vi /etc/my.cnf.d/server.cnf

Insert in the [mariadb-10.1] section the following directives:

binlog_format=ROW
default-storage-engine=innodb
innodb_autoinc_lock_mode=2
innodb_locks_unsafe_for_binlog=1
query_cache_size=1M
query_cache_type=OFF
bind-address=0.0.0.0
datadir=/var/lib/mysql
innodb_log_file_size=100M
innodb_file_per_table
innodb_flush_log_at_trx_commit=2
wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_cluster_address="gcomm://<IP_HOST_G>,<IP_HOST_L>,<IP_HOST_F>"
wsrep_cluster_name='miracle'
wsrep_node_address='<IP_HOST_G>'
wsrep_node_name='<HOST_G>'
wsrep_sst_method=rsync
wsrep_sst_auth=sst_user:[PASSWORD]
enforce_storage_engine='InnoDB'
wsrep_on=ON
sql_mode=''

Adjust the wsrep_node_address and wsrep_node_name variables on HOST_L and HOST_F node:

On HOST_L node:

wsrep_node_address='<IP_HOST_L>’
wsrep_node_name='<HOST_L>'

On HOST_F node:

wsrep_node_address='<IP_HOST_F>'
wsrep_node_name='<HOST_F>'

Start MariaDB with the special ‐‐wsrep-new-cluster option only on the HOST_G node:

# systemctl set-environment MYSQLD_OPTS="--wsrep-new-cluster"
# systemctl start mariadb
# systemctl unset-environment MYSQLD_OPTS

Check cluster status by run the following command on the node:

# mysql
mysql > show status like 'wsrep%'

Start MariaDB on the other cluster node executing the follow command:

# systemctl start mariadb

Using oVirt, add disk on each node of the cluster with the following size:

• HOST_G: 150GB (100GB to databases and 50GB to backup)
• HOST_L: 150GB (100GB to databases and 50GB to backup)
• HOST_F: 220GB (100GB to databases and 120GB to snapshot and backup)

You can find target partition name typing:

# cat /proc/partitions

(in this case /dev/vdb)

First create a physical volumes that will be used to create the LVM:

# pvcreate /dev/vdb

Then create a volume group with name data:

# vgcreate data /dev/vdb

On all nodes create a logical volume named db on data volume group specified dimension by 100GB

# lvcreate -L 100GB -n db data

Build XFS filesystem on /dev/data/db

# mkfs.xfs /dev/data/db

Stop mariadb service:

# systemctl stop mariadb

Mount /dev/data/db

# mount /dev/data/db /mnt

Move all files and folders in /var/lib/mysql/ to /mnt/

# mv /var/lib/mysql/* /mnt/

Make the user mysql and the group mysql the owning user and owning group of the directory /mnt/

# chown mysql:mysql /mnt/

Umount /mnt/ directory

# umount /mnt/

Change /etc/fstab file

# vi /etc/fstab

append the following content:

/dev/data/db		/var/lib/mysql		xfs	noatime		0 0

NOTE: The importance of the noatime setting is that it eliminates the need by the system to make writes to the file system for files which are simply being read.

Mount all filesystems mentioned in fstab:

# mount -a

Start mariadb service:

# systemctl start mariadb

HOST_F is the node designed to backup. The 220GB are assigned as follows:

• 100GB to database
• 100GB to databases backup
• 10GB to snapshot
• 10GB can be used to extend previous logical volumes

The firsts 100GB are assigned to the databases as shown in the previous section.

If HOST_F is down, HOST_L (or HOST_G) is allowed to become a responsable node to backup. So we prepare 50GB to database backup on HOST_G and HOST_L and 100GB on HOST_F.

Create a logical volume named backup on data volume group with 100GB size on HOST_F:

# lvcreate -L 100GB -n backup data

and with max available free size to HOST_G anf HOST_L:

# lvcreate -l 100%FREE -n backup data

Build XFS filesystem on /dev/data/db

# mkfs.xfs /dev/data/backup

Create /backup/mysqldumps directories

# mkdir -p /backup/mysqldumps

Only on HOST_F create a snapshot logical volume that is 10GB in size named /dev/data/db-snap of the origin logical volume named /dev/data/db.

# lvcreate -L 10G -n db-snap -s /dev/data/db

Create /backup/db-snap directory

# mkdir /backup/db-snap

Append the following content to /etc/fstab file:

/dev/data/backup	/backup			xfs	defaults	0 0

On HOST_F append also:

/dev/data/db-snap	/backup/db-snap		xfs	ro,nouuid	0 0

Mount all filesystems mentioned in fstab:

# mount -a