How to set up MySQL or MariaDB high availability with PCS

High availability for a MySQL or MariaDB endpoint reduces downtime by keeping the database service and its client-facing address together during node failure or maintenance. Applications continue using the same host or IP while the cluster relocates the active instance.

The pcs CLI configures Pacemaker resources for a floating IP plus the database daemon. An ocf:heartbeat:IPaddr2 resource adds the floating address, a systemd resource controls the database unit, and a resource group enforces colocation and ordered start/stop so the IP exists before the daemon starts.

Failover moves the service and address; it does not replicate database data. Ensure the storage or replication design keeps the data directory consistent across nodes, and enable fencing to prevent split-brain. Planned failover tests should occur during a maintenance window because active sessions drop during stop/start.

Steps to set up MySQL or MariaDB high availability with PCS:

Confirm the cluster is online with quorum.

$ sudo pcs status
Cluster name: clustername
Cluster Summary:
  * Stack: corosync (Pacemaker is running)
  * Current DC: node-01 (version 2.1.6-6fdc9deea29) - partition with quorum
  * Last updated: Thu Jan  1 05:39:07 2026 on node-01
  * Last change:  Thu Jan  1 05:39:05 2026 by root via cibadmin on node-01
  * 3 nodes configured
  * 0 resource instances configured

Node List:
  * Online: [ node-01 node-02 node-03 ]

Full List of Resources:
  * No resources

Daemon Status:
  corosync: active/enabled
  pacemaker: active/enabled
  pcsd: active/enabled

Identify the database service unit name on each node.

$ systemctl list-unit-files --type=service | grep -E '^(mysql|mysqld|mariadb)\.service'
mariadb.service                              disabled        enabled
mysql.service                                alias           -
mysqld.service                               alias           -

Disable standalone startup for the database service unit on each node.

$ sudo systemctl disable --now mariadb
Synchronizing state of mariadb.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable mariadb
Synchronizing state of mariadb.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable mariadb
Synchronizing state of mariadb.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable mariadb

Stopping the database service interrupts active connections.

Create a floating IP resource for the database endpoint.
```
$ sudo pcs resource create db_ip ocf:heartbeat:IPaddr2 ip=192.0.2.20 cidr_netmask=24 op monitor interval=30s
```
Set nic=<interface> when multiple network interfaces exist.

Related: How to create a floating IP address in Pacemaker
Create the database service resource under systemd control.
```
$ sudo pcs resource create db_service systemd:mariadb op start timeout=120s op stop timeout=120s op monitor interval=30s
```
Use systemd:mysqld or systemd:mysql when those units are present.
Create a resource group for the floating IP resource plus the database service resource.
```
$ sudo pcs resource group add db-stack db_ip db_service
```
Related: How to create a Pacemaker resource group

Verify the resource group is started on a single node.

$ sudo pcs status resources
  * Resource Group: db-stack:
    * db_ip	(ocf:heartbeat:IPaddr2):	 Started node-01
    * db_service	(systemd:mariadb):	 Started node-01

Verify the floating IP address is present on the active node.

$ ip -brief address show
lo               UNKNOWN        127.0.0.1/8 ::1/128 
##### snipped #####
eth0@if456       UP             192.0.2.11/24 192.0.2.20/24

Verify the database service is listening on the expected port on the active node.

$ sudo ss --tcp --listening --numeric --processes
State  Recv-Q Send-Q Local Address:Port  Peer Address:PortProcess
LISTEN 0      80           0.0.0.0:3306       0.0.0.0:*    users:(("mariadbd",pid=196578,fd=24))
##### snipped #####

Run a failover test for the resource group.

Related: How to run a Pacemaker failover test with PCS