HP OpenVMS Systems Documentation

Guidelines for OpenVMS Cluster Configurations

OpenVMS Partners offer a wide selection of tools to meet diverse system management needs, as shown in Table 2-5. The types of tools are described in the following list:

• Enterprise management
  Enables monitoring and management of a heterogeneous environment.
• Schedule managers
  Enable specific actions to be triggered at determined times, including repetitive and periodic activities, such as nightly backups.
• Event managers
  Monitor a system and report occurrences and events that may require an action or that may indicate a critical or alarming situation, such as low memory or an attempted security breakin.
• Console managers
  Enable a remote connection to and emulation of a system console so that system messages can be displayed and commands can be issued.
• Performance managers
  Monitor system performance by collecting and analyzing data to allow proper tailoring and configuration of system resources. Performance managers may also collect historical data for capacity planning.

For current information about OpenVMS Partners and the tools they provide, access the OpenVMS web site:

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

In addition to these utilities and partner products, several commands are available that allow the system manager to set parameters on HSC, HSJ, HSD, HSZ, HSG, and RF subsystems to help configure the system. See the appropriate hardware documentation for more information.

This chapter provides information to help you select systems for your OpenVMS Cluster to satisfy your business and application requirements.

3.1 Alpha, VAX, and HP Integrity Systems

An OpenVMS Cluster can include systems running OpenVMS Alpha or OpenVMS VAX or OpenVMS I64 or a combination of the following two:

• OpenVMS Alpha and OpenVMS VAX
• OpenVMS Alpha and OpenVMS I64

HP provides a full range of systems for the Alpha and VAX architectures. HP supports OpenVMS I64 on several HP Integrity server system models and will be qualified on additional models in the future.

• OpenVMS Alpha operating system
  Based on a 64-bit RISC (reduced instruction set computing) architecture, OpenVMS Alpha provides industry-leading price/performance benefits with standard I/O subsystems for flexibility and expansion.
• OpenVMS VAX operating system
  Based on a 32-bit CISC (complex instruction set computing) architecture, OpenVMS VAX provides high CISC performance and a rich, powerful instruction set. OpenVMS VAX also supports a wide variety of standard I/O subsystems.
• HP OpenVMS I64 operating system
  Based on the Intel® Itanium® architecture, OpenVMS I64 provides the price/performance, reliability, and scalability benefits of OpenVMS on the industry-standard HP Integrity server systems.

Alpha, VAX, and HP Integrity systems span a range of computing environments, including:

• Workstations
• Low-end systems
• Midrange systems
• Enterprise systems

Your choice of systems depends on your business, your application needs, and your budget. With a high-level understanding of systems and their characteristics, you can make better choices.

Table 3-1 is a comparison of recently shipped OpenVMS Cluster systems. While a cluster can provide services to Windows and MS-DOS laptop and personal computers, this topic is not discussed extensively in this manual. For more information about configuring a cluster to serve PCs and laptops, consult your HP representative.

When you choose a system based on scalability, consider the following:

• Maximum processor capacity
• Maximum memory capacity
• Maximum storage capacity

The OpenVMS environment offers a wide range of alternative ways for growing and expanding processing capabilities of a data center, including the following:

• Many Alpha, VAX, and HP Integrity systems can be expanded to include additional memory, processors, or I/O subsystems.
• You can add systems to your OpenVMS Cluster at any time to support increased work load. The vast range of systems, from small workstation to high-end multiprocessor systems, can interconnect and be reconfigured easily to meet growing needs.
• You can add storage to your OpenVMS Cluster system by increasing the quantity and speed of disks, CD-ROM devices, and tapes.
  Reference: For more information about storage devices, see Chapter 5.

Reference: For more information about scalability, see Chapter 10.

3.5 Availability Considerations

An OpenVMS Cluster system is a highly integrated environment in which multiple systems share access to resources. This resource sharing increases the availability of services and data. OpenVMS Cluster systems also offer failover mechanisms that are transparent and automatic, and require little intervention by the system manager or the user.

Reference: See Chapter 8 and Chapter 9 for more information about these failover mechanisms and about availability.

3.6 Performance Considerations

The following factors affect the performance of systems:

• Applications and their performance requirements
• The number of users that the system must support
• The type of storage subsystem that you require

With these requirements in mind, compare the specifications for processor performance, I/O throughput, memory capacity, and disk capacity in the systems that interest you.

3.7 System Specifications

The HP web site provides ordering and configuring information for workstations and servers. It also contains detailed information about storage devices, printers, and network application support.

To access the HP web site, use the following URL:

http://www.hp.com/

An interconnect is a physical path that connects computers to other computers, and to storage subsystems. OpenVMS Cluster systems support a variety of interconnects (also referred to as buses) so that members can communicate with each other and with storage, using the most appropriate and effective method available.

The software that enables OpenVMS Cluster systems to communicate over an interconnect is the System Communications Services (SCS). An interconnect that supports node-to-node SCS communications is called a cluster interconnect. An interconnect that provides node-to-storage connectivity within a cluster is called a shared-storage interconnect. Some interconnects, such as CI and DSSI, can serve as both cluster and storage interconnects.

OpenVMS supports the following types of interconnects:

• Cluster interconnects (node to node only)
  • Ethernet (Alpha, VAX, and I64)
  • Fast Ethernet and Gigabit Ethernet (Alpha and I64)
  • Asynchronous transfer mode (ATM) (Alpha only)
  • FDDI (Fiber Distributed Data Interface) (VAX and Alpha)
  • MEMORY CHANNEL (Alpha only)
  • Shared Memory CI (SMCI) (Galaxy instance to Galaxy instance) (Alpha only)
• Shared-storage interconnects (node to storage only)
  • Fibre Channel (Alpha only)
  • SCSI (Small Computer Systems Interface) (Alpha only and limited to older adapters)
• Both node-to-node and node-to-storage interconnects
  • CI (computer interconnect) (VAX and Alpha)
  • DSSI (Digital Storage Systems Interconnect) (VAX and Alpha)

The interconnects described in this chapter share some general characteristics. Table 4-1 describes these characteristics.

Table 4-2 shows key statistics for a variety of interconnects.

You can use multiple interconnects to achieve the following benefits:

• Failover
  If one interconnect or adapter fails, the node communications automatically move to another interconnect.
• MSCP server load balancing
  In a multiple MSCP server configuration, an OpenVMS Cluster performs load balancing to automatically choose the best path. This reduces the chances that a single adapter could cause an I/O bottleneck. Depending on your configuration, multiple paths from one node to another node may transfer more information than would a single path.
  Reference: See Section 10.7.3 for an example of dynamic MSCP load balancing.

You can use two or more different types of interconnects in an OpenVMS Cluster system. You can use different types of interconnects to combine the advantages of each type and to expand your OpenVMS Cluster system. For example, an Ethernet cluster that requires more storage can expand with the addition of Fibre Channel, SCSI, or CI connections.

4.5 Interconnects Supported by Alpha, VAX, and HP Integrity Systems

Table 4-3 shows the OpenVMS Cluster interconnects supported by Alpha, VAX, and HP Integrity systems.

You can also refer to the most recent OpenVMS Cluster SPD to see the latest information on supported interconnects.