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Applies to SUSE Linux Enterprise High Availability Extension 11 SP4

Part II Configuration and Administration

4 Configuration and Administration Basics

The main purpose of an HA cluster is to manage user services. Typical examples of user services are an Apache Web server or a database. From the user's point of view, the services do something specific when ordered to do so. To the cluster, however, they are only resources which may be started or stopped—the nature of the service is irrelevant to the cluster.

In this chapter, we will introduce some basic concepts you need to know when configuring resources and administering your cluster. The following chapters show you how to execute the main configuration and administration tasks with each of the management tools the High Availability Extension provides.

5 Configuring and Managing Cluster Resources (Web Interface)

In addition to the crm command line tool and the Pacemaker GUI, the High Availability Extension also comes with the HA Web Konsole (Hawk), a Web-based user interface for management tasks. It allows you to monitor and administer your Linux cluster from non-Linux machines as well. Furthermore, it is the ideal solution in case your system only provides a minimal graphical user interface.

This chapter introduces Hawk and covers basic tasks for configuring and managing cluster resources: modifying global cluster options, creating basic and advanced types of resources (groups and clones), configuring constraints, specifying failover nodes and failback nodes, configuring resource monitoring, starting, cleaning up or removing resources, and migrating resources manually. For detailed analysis of the cluster status, Hawk generates a cluster report (hb_report). You can view the cluster history or explore potential failure scenarios with the simulator.

6 Configuring and Managing Cluster Resources (GUI)

This chapter introduces the Pacemaker GUI and covers basic tasks needed when configuring and managing cluster resources: modifying global cluster options, creating basic and advanced types of resources (groups and clones), configuring constraints, specifying failover nodes and failback nodes, configuring resource monitoring, starting, cleaning up or removing resources, and migrating resources manually.

7 Configuring and Managing Cluster Resources (Command Line)

To configure and manage cluster resources, either use the graphical user interface (the Pacemaker GUI) or the crm command line utility. For the GUI approach, refer to Chapter 6, Configuring and Managing Cluster Resources (GUI).

This chapter introduces crm, the command line tool and covers an overview of this tool, how to use templates, and mainly configuring and managing cluster resources: creating basic and advanced types of resources (groups and clones), configuring constraints, specifying failover nodes and failback nodes, configuring resource monitoring, starting, cleaning up or removing resources, and migrating resources manually.

8 Adding or Modifying Resource Agents

All tasks that need to be managed by a cluster must be available as a resource. There are two major groups here to consider: resource agents and STONITH agents. For both categories, you can add your own agents, extending the abilities of the cluster to your own needs.

9 Fencing and STONITH

Fencing is a very important concept in computer clusters for HA (High Availability). A cluster sometimes detects that one of the nodes is behaving strangely and needs to remove it. This is called fencing and is commonly done with a STONITH resource. Fencing may be defined as a method to bring an HA cluster to a known state.

Every resource in a cluster has a state attached. For example: resource r1 is started on alice. In an HA cluster, such a state implies that resource r1 is stopped on all nodes except alice, because the cluster must make sure that every resource may be started on only one node. Every node must report every change that happens to a resource. The cluster state is thus a collection of resource states and node states.

When the state of a node or resource cannot be established with certainty, fencing comes in. Even when the cluster is not aware of what is happening on a given node, fencing can ensure that the node does not run any important resources.

10 Access Control Lists

The cluster administration tools like crm shell (crmsh), Hawk or the Pacemaker GUI can be used by root or any user in the group haclient. By default, these users have full read/write access. To limit access or assign more fine-grained access rights, you can use Access control lists (ACLs).

Access control lists consist of an ordered set of access rules. Each rule allows read or write access or denies access to a part of the cluster configuration. Rules are typically combined to produce a specific role, then users may be assigned to a role that matches their tasks.

11 Network Device Bonding

For many systems, it is desirable to implement network connections that comply to more than the standard data security or availability requirements of a typical Ethernet device. In these cases, several Ethernet devices can be aggregated to a single bonding device.

12 Load Balancing with Linux Virtual Server

The goal of Linux Virtual Server (LVS) is to provide a basic framework that directs network connections to multiple servers that share their workload. Linux Virtual Server is a cluster of servers (one or more load balancers and several real servers for running services) which appears to be one large…

13 Geo Clusters (Multi-Site Clusters)

Apart from local clusters and metro area clusters, SUSE® Linux Enterprise High Availability Extension 11 SP4 also supports geographically dispersed clusters (Geo clusters, sometimes also called multi-site clusters). That means you can have multiple, geographically dispersed sites with a local cluster each. Failover between these clusters is coordinated by a higher level entity, the so-called booth. Support for Geo clusters is available as a separate extension to Geo Clustering for SUSE Linux Enterprise High Availability Extension. For details on how to use and set up Geo clusters, refer to the Quick Start Geo Clustering for SUSE Linux Enterprise High Availability Extension. It is available from http://documentation.suse.com/ or in your installed system under /usr/share/doc/manual/sle-ha-geo-manuals_en/.

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