Corosync/Pacemaker is a supported high availability cluster solution for Oracle Linux 7.3 or newer version. The main component for a Corosync/Pacemaker cluster is to have a reliable fencing agent, to prevent data corruption. The recommended solution is to use a generic fence. There are two agents that can be used: fence_scsi and fence_sbd.
In this blog post we will describe on how to use fence_sbd.
STONITH Block Devices (SBD) use a shared disk that will be used as a fence device. This disk must be used exclusively as sbd device, no filesystem should be created in the disk.
To enable SBD fencing:
1- Install SBD and watchdog (all nodes):
yum install -y watchdog sbd
2- Configure softdog as a watchdog device and start automatic at boot time (all nodes):
echo softdog > /etc/modules-load.d/softdog.conf
3- Change the SBD configuration SBD_DEVICE to point to the shared disk (all nodes):
SBD_DEVICE=”/dev/xvdb” # /dev/xvdb is the shared disk
SBD_OPTS=”-n node1″ # if cluster node name is different from hostname this option must be used
4- Create the SBD device (just in one node)
pcs stonith sbd device setup –device=/dev/xvdb
Enable SBD service (all nodes):
systemctl enable –now sbd
SBD is configured. The Pacemaker STONITH fence can be created (just one node):
pcs stonith create sbd_fencing fence_sbd devices=/dev/xvdb
To test is the SBD is working:
pcs stonith fence node2
node2 should be rebooted.