Guide for High-Availability Cluster Using Pacemaker and Corosync

Creating a high-availability cluster is crucial to ensure continuous uptime for your critical services. In this tutorial, we'll guide you through setting up a high-availability cluster using Pacemaker and Corosync. Pacemaker is an advanced, scalable High-Availability cluster resource manager while Corosync provides the messaging layer, which allows cluster nodes to communicate.

Pacemaker and CoroSync Configuration

Prerequisites

1. Two or more servers with a Linux-based OS installed (we'll use Ubuntu 20.04 for our examples)
2. User with sudo privileges
3. Familiarity with the Linux command line interface

Step 1: Installing Necessary Packages

On each server, start by updating the system and installing necessary software packages.

$ sudo apt update
$ sudo apt upgrade
$ sudo apt install pacemaker corosync

Step 2: Configuring Corosync

The first major step is configuring Corosync. Edit the Corosync configuration file found at /etc/corosync/corosync.conf.

$ sudo nano /etc/corosync/corosync.conf

Enter the following configuration. Replace the bindnetaddr field with your server's network interface address.

totem {
    version: 2
    secauth: off
    cluster_name: cluster_name
    transport: udpu
    interface {
        ringnumber: 0
        bindnetaddr: 192.168.1.1
        mcastport: 5405
    }
}

nodelist {
    node {
        ring0_addr: 192.168.1.1
        nodeid: 1
    }

    node {
        ring0_addr: 192.168.1.2
        nodeid: 2
    }
}

quorum {
    provider: corosync_votequorum
    two_node: 1
}

Step 3: Configuring Pacemaker

In this step, we'll configure Pacemaker on both servers. We'll also ensure that both Pacemaker and Corosync start on boot.

$ sudo systemctl enable pacemaker
$ sudo systemctl enable corosync

Now, restart both services to apply the changes.

$ sudo systemctl restart corosync
$ sudo systemctl restart pacemaker

To check the status of the cluster, use the crm_mon command. It should show both nodes online.

$ crm_mon

Step 4: Adding Resources to the Cluster

In this step, we'll add a service (resource) to the cluster. For demonstration purposes, we'll add a basic IP address.

$ sudo crm configure primitive ClusterIP ocf:heartbeat:IPaddr2 params ip="192.168.1.100" cidr_netmask="32" op monitor interval="30s"

Check the status of your cluster using crm_mon. You should now see the IP address resource in your cluster.

Step 5: Setting Up Resource Groups

If you have more than one resource, it's a good idea to group them together. This ensures that all resources in a group are located on the same node. To create a resource group:

$ sudo crm configure group WebServerGroup ClusterIP

This group can now be managed as a single entity.

This guide provided the basics for setting up a high-availability cluster with Pacemaker and Corosync. There are many more resources and options to explore in the Pacemaker and Corosync documentation.

Relevant Links

• Pacemaker Documentation
• Corosync Documentation

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