This is especially critical if you will install tape devices on the shared SCSI bus. With the exception of the TZ885, TZ887, TL890, TL891, and TL892, tape devices can only be installed at the end of a shared SCSI bus. These tape devices are the only supported tape devices that can be terminated externally.
•Place the devices as close together as possible and ensure that shared SCSI buses will be within length limitations.
•Prepare the systems and storage shelves for the appropriate bus connection, including installing SCSI controllers, UltraSCSI hubs, trilink connectors, and SCSI signal converters.
After you install all necessary cluster hardware and connect the shared SCSI buses, be sure that the systems can recognize and access all the shared disks (see Section 4.3.2). You can then install the TruCluster Server software as described in the TruCluster Server Software Installation manual.
4.1Planning Your TruCluster Server Hardware Configuration
Before you set up a TruCluster Server hardware configuration, you must plan a configuration to meet your performance and availability needs. You must determine the following components for your configuration:
•Number and type of member systems and the number of shared SCSI buses
You can use two to eight member systems for TruCluster Server. A greater number of member systems connected to shared SCSI buses gives you better application performance and more availability. However, all the systems compete for the same buses to service I/O requests, so a greater number of systems decreases I/O performance.
Each member system must have a supported SCSI adapter for each shared SCSI bus connection. There must be enough PCI slots for the Memory Channel cluster interconnect(s) and SCSI adapters. The number of available PCI slots depends on the type of AlphaServer system.
•Cluster interconnects
You need only one cluster interconnect in a cluster. For TruCluster Server Version 5.1, the cluster interconnect is the Memory Channel. However, you can use redundant cluster interconnects to protect against an interconnect failure and for easier hardware maintenance. If you have more than two member systems, you must have one Memory Channel hub for each interconnect.
