Chapter 1 Introduction and Overview

Sun Cluster 3.0 Concepts provides the conceptual information needed by the primary audience for Sun Cluster documentation. This audience includes:

• Service providers who install and service cluster hardware

• System administrators who install, configure, and administer Sun Cluster software

• Application developers who develop data services for applications not currently included with the Sun Cluster product

This book works with the rest of the Sun Cluster documentation set to provide a complete view of Sun Cluster.

This chapter:

• Provides an introduction and high-level overview of Sun Cluster

• Describes the several viewpoints of the Sun Cluster audience

• Identifies key concepts you need to understand before working with Sun Cluster

• Maps key concepts to the Sun Cluster documentation that includes procedures and related information

• Maps cluster-related tasks to the documentation containing procedures used to accomplish those tasks

Introduction to Sun Cluster

Sun Cluster extends the Solaris^TM operating environment into a cluster operating system. A cluster is a collection of loosely coupled computing nodes that provides a single client view of network services or applications, including databases, web services, and file services.

Each cluster node is a standalone server that runs its own processes. These processes can communicate with one another to form what looks like (to a network client) a single system that cooperatively provides applications, system resources, and data to users.

A cluster offers several advantages over traditional single server systems. These advantages include support for highly available and scalable applications, capacity for modular growth, and low entry price compared to traditional hardware fault-tolerant systems.

The goals of Sun Cluster are:

• Reduce or eliminate system downtime because of software or hardware failure

• Ensure availability of data and applications to end users, regardless of the kind of failure that would normally take down a single server system

• Increase application throughput by enabling services to scale to additional processors by adding nodes to the cluster

• Provide enhanced availability of the system by enabling you to perform maintenance without shutting down the entire cluster

High Availability in Sun Cluster

Sun Cluster is designed as a highly available (HA) system, that is, a system that provides near continuous access to data and applications.

By contrast, fault-tolerant hardware systems provide constant access to data and applications, but at a higher cost because of specialized hardware. Additionally, fault-tolerant systems usually do not account for software failures.

Sun Cluster achieves high availability through a combination of hardware and software. Redundant cluster interconnects, storage, and public networks protect against single points of failure. The cluster software continuously monitors the health of member nodes and prevents failing nodes from participating in the cluster to protect against data corruption. Also, the cluster monitors applications and their dependent system resources, and fails over or restarts applications in case of failures.

Refer to "High Availability FAQ" for questions and answers on high availability.

Failover and Scalability in Sun Cluster

Sun Cluster enables you to implement applications on either a failover or scalable basis. Failover and scalable applications can also run on the same cluster concurrently. In general, a failover application provides high availability (redundancy), whereas a scalable application provides high availability along with increased performance. A single cluster can support both failover and scalable applications.

Failover

Failover is the process by which the cluster automatically relocates an application from a failed primary node to a designated secondary node. With failover, Sun Cluster provides high availability.

When a failover occurs, clients might see a brief interruption in service and might need to reconnect after the failover has finished. However, clients are not aware of the physical server from which they are provided the application and data.

Scalability

While failover is concerned with redundancy, scalability provides constant response time or throughput without regard to load. A scalable application leverages the multiple nodes in a cluster to concurrently run an application, thus providing increased performance. In a scalable configuration, each node in the cluster can provide data and process client requests.

Refer to "Data Services" for more specific information on failover and scalable services.

Three Views of Sun Cluster

This section describes three different viewpoints on Sun Cluster and the key concepts and documentation relevant to each viewpoint. These viewpoints come from:

• Hardware installation and service personnel

• System administrators

• Application programmers. Sun Cluster provides a set of highly available data services. These services are applications such as Oracle, Apache Web Server, and DNS that have been configured to become highly available data services running on a cluster. Other applications can be made into highly available data services using the Sun Cluster API. Application programmers can write shell scripts or C programs that use the API.

Hardware Installation and Service Viewpoint

To hardware service people, Sun Cluster looks like a collection of off-the-shelf hardware that includes servers, networks, and storage. These components are all cabled together so that every component has a backup and no single point of failure exists.

Key Concepts - Hardware

Hardware service people need to understand the following cluster concepts.

• Cluster hardware configurations and cabling

• Installing and servicing (adding, removing, replacing):

  • Network interface components (adapters, junctions, cables)

  • Disk interface cards

  • Disk arrays

  • Disk drives

  • The administrative console and the console access device

• Setting up the administrative console and console access device

Suggested Hardware Conceptual References

The following sections contain material relevant to the preceding key concepts:

• "Cluster Nodes"

• "Multihost Disks"

• "Local Disks"

• "Cluster Interconnect"

• "Public Network Interfaces"

• "Client Systems"

• "Administrative Console"

• "Console Access Devices"

• "Clustered Pairs Topology"

• "N+1 (Star) Topology"

Relevant Sun Cluster Documentation

The following Sun Cluster document includes procedures and information associated with hardware service concepts:

• Sun Cluster 3.0 Hardware Guide

System Administrator Viewpoint

To the system administrator, Sun Cluster looks like a set of servers (nodes) cabled together, sharing storage devices. The system administrator sees:

• Specialized cluster software integrated with Solaris software to monitor the connectivity between cluster nodes

• Specialized software to monitor the health of user application programs running on the cluster nodes

• Volume management software to set up and administer disks

• Specialized cluster software to enable all nodes to access all storage devices, even those not directly connected to disks

• Specialized cluster software to enable files to appear on every node as though they were locally attached to that node

Key Concepts - System Administration

System administrators need to understand the following concepts and processes:

• The interaction between the hardware and software components

• The general flow of how to install and configure the cluster including:

  • Installing the Solaris operating environment

  • Installing and configuring Sun Cluster

  • Installing and configuring a volume manager

  • Installing and configuring application software to be cluster ready

  • Installing and configuring Sun Cluster data service software

• Cluster administrative procedures for adding, removing, replacing, and servicing cluster hardware and software components

• Configuration modifications to improve performance

Suggested System Administrator Conceptual References

The following sections contain material relevant to the preceding key concepts:

• "Administrative Interfaces"

• "High-Availability Framework"

• "Global Devices"

• "Disk Device Groups"

• "Global Namespace"

• "Cluster File Systems"

• "Quorum and Quorum Devices"

• "Volume Managers"

• "Data Services"

• "Resources and Resource Types"

• "Public Network Management (PNM) and Network Adapter Failover (NAFO)"

• Chapter 4, Frequently Asked Questions

Relevant Sun Cluster Documentation - System Administrator

The following Sun Cluster documents include procedures and information associated with the system administration concepts:

• Sun Cluster 3.0 Installation Guide

• Sun Cluster 3.0 System Administration Guide

• Sun Cluster 3.0 Error Messages Manual

Application Programmer Viewpoint

Sun Cluster provides several highly available data services for such applications as Oracle, NFS, DNS, iPlanet Web Server, Apache Web Server, and Netscape Directory Server.If a site has to make another application run on a cluster, it can use the Sun Cluster Application Programming Interface (API) and the Data Service Development Library API (DSDL API) to develop the necessary data service software that enables its application to run as a highly available data service on the cluster.

Key Concepts - Application Programmer

Application programmers need to understand the following:

• The characteristics of their application to determine whether it can be made to run as a highly available or scalable data service.

• The Sun Cluster API, DSDL API, and the "generic" data service. Programmers need to determine which tool is most suitable for them to use to write programs or scripts to configure their application for the cluster environment.

Suggested Application Programmer Conceptual References

The following sections contain material relevant to the preceding key concepts:

• "Data Services"

• "Resources and Resource Types"

• Chapter 4, Frequently Asked Questions

Relevant Sun Cluster Documentation - Application Programmer

The following Sun Cluster documents include procedures and information associated with the application programmer concepts:

• Sun Cluster 3.0 Data Services Developers' Guide

• Sun Cluster 3.0 Data Services Installation and Configuration Guide

Sun Cluster Tasks

All concepts map into tasks and all tasks require some conceptual background. The following table provides a high-level view of the tasks and the documentation that describes task steps. The concepts sections in this book describe how the concepts map to these tasks.

Table 1-1 Task Map: Mapping User Tasks to Documentation

To Do This Task...	Use This Documentation...
Install cluster hardware	Sun Cluster 3.0 Hardware Guide
Install Solaris software on the cluster	Sun Cluster 3.0 Installation Guide
Install SunTM Management Center software	Sun Cluster 3.0 Installation Guide
Install and configure Sun Cluster software	Sun Cluster 3.0 Installation Guide
Install and configure volume management software	Sun Cluster 3.0 Installation Guide Your volume management documentation
Install and configure Sun Cluster data services	Sun Cluster 3.0 Data Services Installation and Configuration Guide
Service cluster hardware	Sun Cluster 3.0 Hardware Guide
Administer Sun Cluster software	Sun Cluster 3.0 System Administration Guide
Administer volume management software	Sun Cluster 3.0 System Administration Guide and your volume management documentation
Administer application software	Your application documentation
Problem identification and suggested user actions	Sun Cluster 3.0 Error Messages Manual
Create a new data service	Sun Cluster 3.0 Data Services Developers' Guide