[RHEL8] Redhat Pacemaker PCS Cluster

History of PCS:--->

PCS (Pacemaker Configuration System) is a command line and web-based interface for configuring and managing Pacemaker clusters. It was first introduced as a part of the Pacemaker project, which was started in the year 2005 by Linux-HA (Linux High Availability) community. PCS was designed to provide a more user-friendly interface for performing common cluster operations and to simplify the process of creating and maintaining a cluster configuration.

In the year 2010, PCS was included as a part of Red Hat Enterprise Linux (RHEL) 6 and also in various other Linux distributions. Over the years, PCS has gone through various updates and new features were added to it. With each new release, it has become more robust, secure, and easy to use.

With the release of RHEL 8 and later, PCS was re-designed with new features and improvements, such as support for new platforms, improved security, and enhanced scalability.

PCS is also an open-source software and it is actively being developed and maintained by the Linux-HA community and Red Hat. It is widely used by organizations and IT administrators to manage and maintain high availability clusters in their production environments.

Redhat Pacemaker PCS Cluster:--->

Red Hat Pacemaker is a cluster resource manager for Linux-based systems. It is used to create and manage highly-available clusters by controlling the start, stop, and failover of resources such as services and virtual IP addresses. PCS (Pacemaker Configuration System) is a command line and web-based interface for configuring and managing Pacemaker clusters. It provides a simplified way to create, manage and maintain a cluster configuration, as well as a more user-friendly interface for performing common cluster operations. Together, Pacemaker and PCS are a powerful tool for creating and managing highly-available clusters on Red Hat Enterprise Linux.

Failover of resources such as services and virtual IP addresses:--->

Failover in the context of Pacemaker and PCS refers to the process of automatically switching over to a secondary resource or node in the event of a failure or outage of the primary resource or node. This ensures that the service or resource remains available and accessible to users, even if one of the nodes or resources in the cluster goes down.

For example, a service such as a web server may be running on a primary node in a cluster. If that primary node goes down, Pacemaker will automatically failover to a secondary node, ensuring that the web server is still available for users to access. Similarly, a virtual IP address can be configured to failover to a secondary node in the event that the primary node it is associated with goes down.

Failover in Pacemaker and PCS is achieved through the use of "resources" and "resource agents". Resources are the services and resources that are being managed by Pacemaker (such as a web server, database, or virtual IP address), and resource agents are scripts that are used to control the behavior of those resources (such as starting, stopping, or checking the status of a service).