Document revision date: 30 March 2001
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Guidelines for OpenVMS Cluster Configurations

Guidelines for OpenVMS Cluster Configurations

Order Number: AA--Q28LE--TK

April 2001

OpenVMS Cluster availability, scalability, and system management benefits are highly dependent on configurations, applications, and operating environments. This guide provides suggestions and guidelines to help you maximize these benefits.

Revision/Update Information: This manual supersedes Guidelines for OpenVMS Cluster Configurations Version 7.2-1.

Software Version: OpenVMS Alpha Version 7.3
OpenVMS VAX Version 7.3

Compaq Computer Corporation
Houston, Texas

© 2001 Compaq Computer Corporation

COMPAQ, VAX, VMS, and the Compaq logo Registered in the U.S. Patent and Trademark Office.

OpenVMS is a trademark of Compaq Information Technologies Group, L.P. in the United States and other countries.

Motif, OSF/1, and UNIX are trademarks of The Open Group in the United States and other countries.

Microsoft, MS-DOS, Visual C++, Windows, and Windows NT are trademarks of Microsoft Corporation in the United States and other countries.

All other product names mentioned herein may be the trademarks of their respective companies.

Confidential computer software. Valid license from Compaq required for possession, use, or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor's standard commercial license.

Compaq shall not be liable for technical or editorial errors or omissions contained herein. The information in this document is subject to change without notice.

Compaq shall not be liable for technical or editorial errors or omissions contained herein. The information in this document is provided "as is" without warranty of any kind and is subject to change without notice. The warranties for Compaq products are set forth in the express limited warranty statements accompanying such products. Nothing herein should be construed as constituting an additional warranty.


The Compaq OpenVMS documentation set is available on CD-ROM.

Contents Index


This document can help you design an OpenVMS Cluster configuration to suit your business, application, and computing needs.

It provides information to help you choose systems, interconnects, storage devices, and software. It can also help you combine these components to achieve high availability, scalability, performance, and ease of system management.

Intended Audience

This document is for people who purchase or recommend the purchase of OpenVMS Cluster products and for people who configure OpenVMS Cluster systems. It assumes a basic understanding of computers and OpenVMS Cluster concepts.

About This Guide

OpenVMS Cluster systems are designed to act as a single virtual system, even though they are made up of many components and features, as shown in Figure 1.

Figure 1 OpenVMS Cluster System Components and Features

Understanding the components and features of an OpenVMS Cluster configuration can help you to get the most out of your cluster. Table 1 shows how this guide is organized to explain these cluster concepts.

Table 1 Document Organization
Read... Chapter Title So that you can...
Chapter 1 Overview of OpenVMS Cluster System Configurations Understand OpenVMS Cluster hardware, software, and general concepts
Chapter 2 Determining Business and Application Requirements Learn to analyze your business and application needs and how they apply to your cluster
Chapter 3 Choosing OpenVMS Cluster Systems Understand your computer requirements and make appropriate choices
Chapter 4 Choosing OpenVMS Cluster Interconnects Learn about cluster interconnects and make appropriate choices
Chapter 5 Choosing OpenVMS Cluster Storage Subsystems Learn to analyze your storage requirements and make appropriate choices
Chapter 6 Configuring Multiple Paths to SCSI and Fibre Channel Storage Learn how to configure multiple paths to storage using Parallel SCSI or Fibre Channel interconnects, thereby increasing availability
Chapter 7 Configuring Fibre Channel as an OpenVMS Cluster Storage Interconnect Learn how to configure an OpenVMS Cluster with Fibre Channel as a storage interconnect
Chapter 8 Configuring OpenVMS Clusters for Availability Understand how to increase the availability of a cluster system
Chapter 9 Configuring CI OpenVMS Clusters for Availability and Performance Learn how to use multiple components and advanced techniques to obtain high levels of availability and performance
Chapter 10 Configuring OpenVMS Clusters for Scalability Learn how to expand an OpenVMS Cluster system in all of its dimensions, while understanding the tradeoffs
Chapter 11 OpenVMS Cluster System Management Strategies Understand and deal effectively with some of the issues involved in managing an OpenVMS Cluster system
Appendix A SCSI As an OpenVMS Cluster Interconnect Configure multiple hosts and storage on a single SCSI bus so that multiple VAX and Alpha hosts can share access to SCSI devices directly
Appendix B MEMORY CHANNEL Technical Summary Learn why, when, and how to use the MEMORY CHANNEL interconnect
Appendix C CI-to-PCI Adapter (CIPCA) Technical Summary Learn why, when, and how to use the CIPCA adapter
Appendix D Multiple-Site OpenVMS Clusters Understand the benefits, the configuration options and requirements, and the management of multiple-site OpenVMS Cluster systems

Related Documents

For additional information on the topics covered in this manual, refer to the following documents:

For additional information about the OpenVMS products and services, access the Compaq World Wide Web address: 

Reader's Comments

Compaq welcomes your comments on this manual. Please send comments to either of the following addresses:
Mail Compaq Computer Corporation
OSSG Documentation Group, ZKO3-4/U08
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Nashua, NH 03062-2698

How To Order Additional Documentation

Use the following World Wide Web address to order additional documentation:

If you need help deciding which documentation best meets your needs, call 800-282-6672).


VMScluster systems are now referred to as OpenVMS Cluster systems. Unless otherwise specified, references to OpenVMS Clusters or clusters in this document are synonymous with VMSclusters.

In this manual, every use of DECwindows and DECwindows Motif refers to DECwindows Motif for OpenVMS software.

The following conventions are also used in this manual:
Ctrl/ x A sequence such as Ctrl/ x indicates that you must hold down the key labeled Ctrl while you press another key or a pointing device button.
PF1 x A sequence such as PF1 x indicates that you must first press and release the key labeled PF1 and then press and release another key or a pointing device button.
[Return] In examples, a key name enclosed in a box indicates that you press a key on the keyboard. (In text, a key name is not enclosed in a box.)

In the HTML version of this document, this convention appears as brackets, rather than a box.

... A horizontal ellipsis in examples indicates one of the following possibilities:
  • Additional optional arguments in a statement have been omitted.
  • The preceding item or items can be repeated one or more times.
  • Additional parameters, values, or other information can be entered.
A vertical ellipsis indicates the omission of items from a code example or command format; the items are omitted because they are not important to the topic being discussed.
( ) In command format descriptions, parentheses indicate that you must enclose the options in parentheses if you choose more than one.
[ ] In command format descriptions, brackets indicate optional elements. You can choose one or more options, or no options. (Note, however, that brackets are not optional in the syntax of a directory name in an OpenVMS file specification or in the syntax of a substring specification in an assignment statement.)
[|] In command format descriptions, vertical bars separating items inside brackets indicate that you choose one, none, or more than one of the options.
{ } In command format descriptions, braces indicate a required choice of options; you must choose one of the options listed.
bold text This text style represents the introduction of a new term or the name of an argument, an attribute, or a reason.
italic text Italic text indicates important information, complete titles of manuals, or variables. Variables include information that varies in system output (Internal error number), in command lines (/PRODUCER= name), and in command parameters in text (where dd represents the predefined code for the device type).
UPPERCASE TEXT Uppercase text indicates a command, the name of a routine, the name of a file, or the abbreviation for a system privilege.
Monospace text Monospace type indicates code examples and interactive screen displays.
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Chapter 1
Overview of OpenVMS Cluster System Configuration

This chapter contains information about OpenVMS Cluster hardware and software components, as well as general configuration rules.

1.1 Mixed Alpha and VAX Clusters

An OpenVMS Cluster is a group of OpenVMS Alpha and OpenVMS VAX systems, storage subsystems, interconnects, and software that work together as one virtual system.

In an OpenVMS Cluster system, each Alpha and VAX node:

In addition, an OpenVMS Cluster system is managed as a single entity.

Table 1-1 shows the benefits that an OpenVMS Cluster system offers.

Table 1-1 OpenVMS Cluster System Benefits
Benefit Description
Resource sharing Multiple systems can access the same storage devices, so that users can share files clusterwide. You can also distribute applications, batch, and print-job processing across multiple systems. Jobs that access shared resources can execute on any system.
Availability Data and applications remain available during scheduled or unscheduled downtime of individual systems. A variety of configurations provide many levels of availability up to and including disaster-tolerant operation.
Flexibility OpenVMS Cluster computing environments offer compatible hardware and software across a wide price and performance range.
Scalability You can add processing and storage resources without disturbing the rest of the system. The full range of systems, from high-end symmetric multiprocessing (SMP) systems to smaller workstations, can be interconnected and easily reconfigured to meet growing needs. You control the level of performance and availability as you expand.
Ease of management OpenVMS Cluster management is efficient and secure. Because you manage an OpenVMS Cluster as a single system, many tasks need to be performed only once. OpenVMS Clusters automatically balance user, batch, and print work loads.
Open systems Adherence to IEEE, POSIX, OSF/1, Motif, OSF DCE, ANSI SQL, and TCP/IP standards provides OpenVMS Cluster systems with application portability and interoperability.

1.2 Hardware Components

An OpenVMS Cluster system comprises many hardware components, such as systems, interconnects, adapters, storage subsystems, and peripheral devices. Table 1-2 describes these components and provides examples.

Table 1-2 Hardware Components in an OpenVMS Cluster System
Components Description Examples
System A cabinet that contains one or more processors, memory, and input/output (I/O) adapters that act as a single processing body.

Reference: See Chapter 3 for more information about OpenVMS systems.

OpenVMS Cluster systems can contain any supported Alpha, VAX, or MicroVAX system, including SMP systems.
Interconnect The hardware connection between OpenVMS Cluster nodes over which the nodes communicate.

Reference: See Chapter 4 for more information about OpenVMS Cluster interconnects.

An OpenVMS Cluster system can have one or more of the following interconnects:
  • CI
  • Digital Storage Systems Interconnect (DSSI)
  • Fiber Distributed Data Interface (FDDI)
  • Small Computer Systems Interface (SCSI)
  • Fibre Channel
  • Ethernet, Fast Ethernet, Gigabit Ethernet
  • ATM (asynchronous transfer mode)
Storage subsystems Devices on which data is stored and the optional controllers that manage the devices.

Reference: See Chapter 5 for more information about OpenVMS storage subsystems.

Storage subsystems can include:
  • SCSI disks and tapes
  • SDI, STI disks and tapes
  • Storage array cabinets
  • SDI/STI and SCSI storage controllers
  • InfoServer systems
Adapter Devices that connect nodes in an OpenVMS Cluster to interconnects and storage.

Reference: See Chapter 4 for more information about adapters.

The following adapters are used on Peripheral Component Interconnect (PCI) systems:
  • CIPCA (CI)
  • DE435 (Ethernet)
  • KGPSA (Fibre Channel)
  • DEGPA (Gigabit Ethernet)
Peripheral devices Devices that provide input to and produce output from a system. Peripheral devices include:
  • Terminals, terminal servers, and modems
  • Printers, plotters

1.3 Software Components

OpenVMS Cluster system software can be divided into the following types:

1.3.1 OpenVMS Operating System Components

The operating system manages proper operation of hardware and software components and resources.

Table 1-3 describes the operating system components necessary for OpenVMS Cluster operations. All of these components are enabled by an OpenVMS operating system license or an OpenVMS Cluster license.

Table 1-3 Operating System Components
Component Function
Record Management Services (RMS) and OpenVMS file system Provide shared read and write access to files on disks and tapes in an OpenVMS Cluster environment.
Clusterwide process services Enables clusterwide operation of OpenVMS commands, such as SHOW SYSTEM and SHOW USERS, as well as the ability to create and delete processes clusterwide.
Distributed Lock Manager Synchronizes access by many users to shared resources.
Distributed Job Controller Enables clusterwide sharing of batch and print queues, which optimizes the use of these resources.
Connection Manager Controls the membership and quorum of the OpenVMS Cluster members.
SCS (System Communications Services) Implements OpenVMS Cluster communications between nodes using Compaq's System Communications Architecture (SCA).
MSCP server Makes locally connected disks to which it has direct access available to other systems in the OpenVMS Cluster.
TMSCP server Makes locally connected tapes to which it has direct access available to other systems in the OpenVMS Cluster.

Figure 1-1 shows how the hardware and operating system components fit together in a typical OpenVMS Cluster system.

Figure 1-1 Hardware and Operating System Components

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