Red Hat CLUSTER FOR ENTERPRISE LINUX 5.0 Installationsanleitung PDF herunterladen (Seite 11)

Chapter 1. High Availability Add-On Overview

The High Availability Add-On is a clustered system that provides reliability, scalability, and

availability to critical production services. The following sections provide a high-level description of

the components and functions of the High Availability Add-On:

Section 1.1, “Cluster Basics”

Section 1.2, “ High Availability Add-On Introduction”

Section 1.3, “ Cluster Infrastructure”

1.1. Clust er Basics

A cluster is two or more computers (called nodes or members) that work together to perform a task.

There are four major types of clusters:

Storage

High availability

Load balancing

High performance

Storage clusters provide a consistent file system image across servers in a cluster, allowing the

servers to simultaneously read and write to a single shared file system. A storage cluster simplifies

storage administration by limiting the installation and patching of applications to one file system.

Also, with a cluster-wide file system, a storage cluster eliminates the need for redundant copies of

application data and simplifies backup and disaster recovery. The High Availability Add-On provides

storage clustering in conjunction with Red Hat GFS2 (part of the Resilient Storage Add-On).

High availability clusters provide highly available services by eliminating single points of failure and

by failing over services from one cluster node to another in case a node becomes inoperative.

Typically, services in a high availability cluster read and write data (via read-write mounted file

systems). Therefore, a high availability cluster must maintain data integrity as one cluster node takes

over control of a service from another cluster node. Node failures in a high availability cluster are not

visible from clients outside the cluster. (high availability clusters are sometimes referred to as failover

clusters.) The High Availability Add-On provides high availability clustering through its High

Availability Service Management component, rg manag er.

Load-balancing clusters dispatch network service requests to multiple cluster nodes to balance the

request load among the cluster nodes. Load balancing provides cost-effective scalability because

you can match the number of nodes according to load requirements. If a node in a load-balancing

cluster becomes inoperative, the load-balancing software detects the failure and redirects requests to

other cluster nodes. Node failures in a load-balancing cluster are not visible from clients outside the

cluster. Load balancing is available with the Load Balancer Add-On.

High-performance clusters use cluster nodes to perform concurrent calculations. A high-performance

cluster allows applications to work in parallel, therefore enhancing the performance of the

applications. (High performance clusters are also referred to as computational clusters or grid

computing.)

⁠Chapt er 1 . High Availabilit y Add- O n Overview

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 38 39

Keine Kommentare

Red Hat CLUSTER FOR ENTERPRISE LINUX 5.0 Installationsanleitung Seite 11