Table 1-4 describes the optional networking software that enables OpenVMS Cluster system nodes to communicate and share resources with other OpenVMS Cluster nodes.

Table 1-4 OpenVMS Cluster Networking Components

Optional Software	Function
DECnet-Plus/DECnet	A network transport is necessary for internode communication.
Distributed File Service (DFS)	Software to let you communicate and share resources among systems over extended distances.
HP Advanced Server for OpenVMS (Advanced Server) and HP Common Internet File System (CIFS) for OpenVMS	Client and server networking software that links PC systems into OpenVMS Cluster systems. Advanced Server can be used on only Alpha systems and CIFS can be used for both Integrity servers and Alpha systems.
HP TCP/IP Services for OpenVMS software	Provides Network File System (NFS) server capabilities for OpenVMS and supports Internet networking protocols. Cluster over IP requires TCP/IP stack for cluster communication.

1.3.3 Storage Enhancement Software

Optional storage enhancement software improves the performance or availability of storage subsystems.

Examples include:

• Volume Shadowing for OpenVMS (redundant arrays of independent disks [RAID] level 1)
• DECram for OpenVMS (random access memory [RAM] disk)
• RAID Software for OpenVMS (supports RAID level 0 arrays (disk striping) and RAID level 5 arrays (disk striping with parity)
• Hierarchical Storage Manager (HSM)

For the latest information about OpenVMS storage management products, refer to the OpenVMS Products page of the OpenVMS web site:

http://www.hp.com/go/openvms

1.3.4 System Management Software

System management software helps you manage your OpenVMS Cluster system.

Examples include:

• HP Archive/Backup System for OpenVMS
• HP Code Management System for OpenVMS
• HP WBEM Services for OpenVMS Integrity servers

To take advantage of OpenVMS Cluster features and benefits, proper configuration is essential. An ideal OpenVMS Cluster configuration meets the following criteria:

• Provides the best combination of hardware and software components to meet your business requirements.
• Strategically distributes your budget dollars to return maximum value in the areas that are high priority for your business.
• Meets your current needs and retains your investment as your business needs grow and change.

Configuring your OpenVMS Cluster system requires careful planning because you need to consider many factors. You will probably modify plans as new factors arise. As your design evolves, you can weigh advantages against tradeoffs and make decisions that best meet your needs.

1.4.1 General Configuration Rules

The following general rules apply to OpenVMS Cluster systems:

• An OpenVMS Cluster system consisting of Integrity server systems and Alpha cannot contain more than 96 (combined total) systems.
• An Alpha and an Integrity server system cannot boot from the same system disk. System disks are architecture specific and can be shared only by systems of the same architecture.
• Each OpenVMS node must be able to communicate directly with every other OpenVMS Cluster node.
  Configurations that use a shared (multihost) SCSI bus or a shared (multihost) Fibre Channel interconnect must also be configured with any of the other supported OpenVMS Cluster interconnects, because node-to-node communication does not occur across the SCSI bus or the Fibre Channel.
  Reference: See Section 4.8 for more information about the SCSI interconnect and Section 4.6 for more information about the Fibre Channel interconnect.
  Configurations that use SAS interconnect must also be configured with any of the other supported OpenVMS Cluster interconnects.
  Reference: See Section 4.9 for more information about the SAS interconnect.
• An OpenVMS Cluster node or storage device can participate in only one OpenVMS Cluster system at a time.
• DECnet-Plus software is not required in an OpenVMS Cluster configuration. However, DECnet-Plus is necessary if internode process-to-process communication using DECnet mailboxes is needed.
• Cluster over IP requires TCP/IP Services. If any node requires IP for cluster communication, all the other members must be enabled for IP.

In addition to these general rules, more detailed guidelines apply to different configurations. The rest of this manual discusses those guidelines in the context of specific configurations.

This chapter contains information about how to determine your OpenVMS Cluster business and application requirements.

2.1 Determining Business Requirements

The kinds of business requirements that you have affect the way that you configure your OpenVMS Cluster. Typical business requirements for an OpenVMS Cluster system include:

• Budget
• Availability
• Scalability and future growth
• Physical location requirements
• Security

Some of these requirements may conflict with each other, such as scalability and physical location. For example, you may want to grow your OpenVMS Cluster, but you are limited by physical space or by the location of your systems. In situations like this, determine what your primary requirements are and where you are willing to make tradeoffs.

2.1.1 Budget

As with most business decisions, many of your choices will be determined by cost. Prioritizing your requirements can help you apply your budget resources to areas with the greatest business needs.

When determining your budget, plan for the initial system cost as well as the cost of ownership, which includes:

• Service and update
• Power consumption
• Cooling
• System management

Determine how available your computing system must be. Most organizations fall into one of the three broad (and sometimes overlapping) categories shown in Table 2-1.

Table 2-1 Availability Requirements

Availability Requirements	Description
Conventional	For business functions that can wait with little or no effect while a system or application is unavailable.
24 x 365	For business functions that require uninterrupted computing services, either during essential time periods or during most hours of the day throughout the year. Minimal down time is acceptable.
Disaster tolerant	For business functions with extremely stringent availability requirements. These businesses need to be immune to disasters like earthquakes, floods, and power failures.

Reference: For more information about availability, see Chapter 8 in this guide.

2.1.3 Scalability and Future Growth

Scalability is the ability to expand an OpenVMS Cluster in any system, storage, and interconnect dimension and at the same time fully use the initial configuration equipment. Scalability at the node level means being able to upgrade and add to your node's hardware and software. Scalability at the OpenVMS Cluster level means being able to increase the capacity of your entire OpenVMS Cluster system by adding processing power, interconnects, and storage across many nodes.

HP offers a full range of Alpha and Integrity systems, with each supporting different processing, storage, and interconnect characteristics. Investing in the appropriate level means choosing systems that meet and perhaps exceed your current business requirements with some extra capacity to spare. The extra capacity is for future growth, because designing too close to your current needs can limit or reduce the scalability of your OpenVMS Cluster.

If you design with future growth in mind, you can make the most of your initial investment, reuse original equipment, and avoid unnecessary upgrades later.

Reference: See Chapter 9 for more help with analyzing your scalability requirements.

2.1.4 Physical Location Requirements

Physical restrictions can play a key role in how you configure your OpenVMS Cluster. Designing a cluster for a small computer room or office area is quite different from designing one that will be spread throughout a building or across several miles. Power and air-conditioning requirements can also affect configuration design.

You may want to allow room for physical growth and increased power and cooling requirements when designing your cluster.

Reference: See Section 8.6 and Section 9.3.8 for information about multiple and extended local area network (LAN) configurations.

For information about clusters formed using IP at different geographical locations, see Section C.2.

2.1.5 Security

A secure environment is one that limits physical and electronic access to systems by unauthorized users. Most businesses can achieve a secure environment with little or no performance overhead. However, if security is your highest priority, you may need to make tradeoffs in convenience, cost, and performance.

Reference: See the HP OpenVMS Guide to System Security Guide for more information.

2.2 Determining Application Requirements

Applications require processing power, memory, storage, and I/O resources. Determining your application requirements allows you to design an OpenVMS Cluster system that will meet your application needs. To determine your application requirements, follow the steps described in Table 2-2.

Table 2-2 Determining Your Application Requirements

Step	Description
1	Make a list of the applications you currently run or expect to run.
2	For each application, write down your processor, memory, and I/O requirements (the application documentation provides this information.) Processor power must be proportional to the number of calculations your applications perform, with enough additional processor power to oversee data transfer between nodes and between nodes and storage. Memory capacity must be sufficient for your applications and for additional OpenVMS Cluster functions. Extra memory frequently improves system performance, so an initial investment in extra memory is probably a good one. I/O performance requirements differ among applications. As you choose components such as nodes, interconnects, and adapters, monitor the inherent speed of each component so that you can choose faster components and eliminate potential bottlenecks.
3	Add up the CPU, memory, and I/O requirements for all of your applications. Add to this sum any special requirements, such as user requirements and peripheral devices.
4	When you have determined your total application requirements, be sure that your CPU, memory, and I/O resources exceed these requirements by 20%.

2.2.1 Adding Memory

Systems require approximately 5% more memory to run in an OpenVMS Cluster than to run standalone. This additional memory is used to support the shared cluster resource base, which is larger than in a standalone configuration.

With added memory, a node in an OpenVMS Cluster generally can support the same number of users or applications that it supported as a standalone system. As a cluster configuration grows, the amount of memory used for system work by each node may increase. Because the per-node increase depends on both the level of data sharing in the cluster and the distribution of resource management, that increase does not follow fixed rules. If the node is a resource manager for a heavily used resource, additional memory may increase performance for cluster users of that resource.

Reference: See the Software Product Description for the memory requirements.

2.2.2 Balancing Processor, Memory, and I/O Resources

Application performance depends on adequate processor, memory, and I/O resources. Depending on your applications, one of these resources may be more important than the others. Consider your application requirements, and find a balance among these three resources that meets your requirements. Table 2-3 provides some guidelines on the resource requirements of different application types.

Table 2-3 Resource Requirements of Application Types

Application Type	Example	Requirement
General timesharing	Program development, document preparation, office automation	Processor and I/O intensive
Searching and updating a database and displaying reports	Transaction processing, funds transfer, online order entry or reservation systems	I/O and memory intensive
Simulation, modeling, or calculation	Computer-aided design and manufacturing, image processing, graphics applications	Processor and memory intensive

2.2.3 System Management Tools and Utilities

The OpenVMS operating system supports a number of utilities and tools that help you determine your business and application requirements in OpenVMS Cluster configurations. Table 2-4 describes many of these products. All are supplied with the OpenVMS operating system except for Disaster Tolerant Cluster Services (DTCS), which are customized for each environment. You can learn more about DTCS from your HP service representative and from the DTCS web site:

http://h71000.www7.hp.com/availability/

Table 2-4 System Management Tools from HP

Tool	Function
Accounting utility	Tracks how resources are being used.
AUTOGEN command procedure	Optimizes system parameter settings based on usage.
Availability Manager	HP Availability Manager is a system management tool that enables one or more OpenVMS Integrity server or Alpha nodes to be monitored extended LAN or wide area network (WAN). That is, the nodes for which you are collecting the information must be in the same extended LAN and there should be an interface that communicates with the collector nodes as well as the WAN analyzer. The Availability Manager collects system and process data from multiple OpenVMS nodes simultaneously, and then analyzes the data and displays the output using a native Java GUI.
HP Insight Management Agents for OpenVMS	Enables you to look at devices on your OpenVMS systems. With the installation of Insight Manager on a Microsoft Windows server, you can manage all your platforms from a single Windows server.
HP WBEM Services for OpenVMS	WBEM (Web-Based Enterprise Management) enables management applications to retrieve system information and request system operations wherever and whenever required. It allows customers to manage their systems consistently across multiple platforms and operating systems, providing integrated solutions that optimize your infrastructure for greater operational efficiency.
Disaster Tolerant Cluster Services (DTCS)	Tools and customized services for configuring and managing disaster-tolerant clusters that span different geographic sites.
Monitor utility	Provides basic performance data.
OpenVMS Data Collector and Performance Analyzer (ECP Data Collector and ECP Performance Analyzer)	The rights to use these ECP products are provided at no additional costs. The ECP Data Collector provides performance-data collection, archiving, reporting, and file display. The ECP Performance Analyzer assists in performance analysis and capacity planning of OpenVMS Cluster systems by identifying bottlenecks and recommending ways to fix problems. An API is provided within the Data Collector to gain direct access to the data it collects.
Performance Data Collector for OpenVMS (TDC V2)	Used to gather performance data for an AlphaServer system running OpenVMS Version 7.3-2, or later. By default, TDC periodically collects and stores data in a file. Subsequently, user applications can retrieve data from the file.
Show Cluster utility	Monitors activity and performance in a OpenVMS Cluster configuration.
Systems Communications Architecture Control Program (SCACP)	Designed to monitor and manage LAN cluster communications.

For more information about Availability Manager, Performance Data Collector for OpenVMS (TDC V2), and the OpenVMS Management Station, see the following web site:

http://h71000.www7.hp.com/openvms/system_management.html

For more information about the Accounting utility, the AUTOGEN command procedure, the Monitor utility, the Show Cluster utility, and the System Communications Architecture Control Program (SCACP), refer to the OpenVMS System Management Utilities Reference Manual.