Configuring the Cluster Layout

The following task describes how to create a cluster, add nodes, and configure the chosen heartbeat mode. Run the commands on a single host that you want to be a node in the cluster.

The examples shown create a cluster called mycluster, with the following hostnames and IP addresses as nodes in the cluster:

ol-sys0: 10.1.0.100
ol-sys1: 10.1.0.110
ol-sys2: 10.1.0.120

Define the cluster.
Create a cluster definition by running the following command on any node:
```
sudo o2cb add-cluster cluster-name
```
For example, to create the cluster mycluster from the ol-sys1 host, run the following command on ol-sys1:
```
sudo o2cb add-cluster mycluster
```
Add nodes to the cluster.
Add the current host and all other required hosts as nodes to the cluster.
```
sudo o2cb add-node cluster-name hostname --ip ip_address
```
The IP address is the IP address that's used by the node for private communication in the cluster.

For example, to add nodes to mycluster from ol-sys1, you would type the following commands on ol-sys1:
```
sudo o2cb add-node mycluster ol-sys0 --ip 10.1.0.100
sudo o2cb add-node mycluster ol-sys1 --ip 10.1.0.110
sudo o2cb add-node mycluster ol-sys2 --ip 10.1.0.120
```
Note:

OCFS2 only works with IPv4 addresses.
(Optional) Configure the global heartbeat mode.
The default heartbeat mode for the cluster is local. If you want the cluster to run in global heartbeat mode, do the following:
1. Run the following command on every cluster device:
```
sudo o2cb add-heartbeat cluster-name device-name
```
  For example, for mycluster, you set the cluster heartbeat on /dev/sdd, /dev/sdg, and /dev/sdj as follows:
```
sudo o2cb add-heartbeat mycluster /dev/sdd
sudo o2cb add-heartbeat mycluster /dev/sdg
sudo o2cb add-heartbeat mycluster /dev/sdj
```
2. Set the cluster's heartbeat mode to global.
```
sudo o2cb heartbeat-mode cluster-name global
```
Important:

You must configure the global heartbeat feature to use whole disk devices. You can't use disk partitions for global heartbeat mode.
Copy the cluster configuration file to each cluster node.

Copy the cluster /etc/ocfs2/cluster.conf file to each node in the cluster.

(Optional) Show information about the cluster.

Run the following command to display information about the cluster:

sudo o2cb list-cluster cluster-name

A three-node cluster with a global heartbeat would display information similar to the following:

node:
       name = ol-sys0
       cluster = mycluster
       number = 0
       ip_address = 10.1.0.100
       ip_port = 7777

node:
       name = ol-sys1
       cluster = mycluster
       number = 1
       ip_address = 10.1.0.110
       ip_port = 7777

node:
       name = ol-sys2
       cluster = mycluster
       number = 2
       ip_address = 10.1.0.120
       ip_port = 7777

cluster:
       name = mycluster
       heartbeat_mode = global
       node_count = 3

heartbeat:
       cluster = mycluster
       region = 7DA5015346C245E6A41AA85E2E7EA3CF

heartbeat:
       cluster = mycluster
       region = 4F9FBB0D9B6341729F21A8891B9A05BD

heartbeat:
       cluster = mycluster
       region = B423C7EEE9FC426790FC411972C91CC3

The heartbeat regions are represented by the UUIDs of their block devices.

The same cluster mycluster with a local heartbeat would display the following information:

node:
       name = ol-sys0
       cluster = mycluster
       number = 0
       ip_address = 10.1.0.100
       ip_port = 7777
  
node:
       name = ol-sys1
       cluster = mycluster
       number = 1
       ip_address = 10.1.0.110
       ip_port = 7777
  
node:
       name = ol-sys2
       cluster = mycluster
       number = 2
       ip_address = 10.1.0.120
       ip_port = 7777
  
cluster:
       name = mycluster
       heartbeat_mode = local
       node_count = 3