When configuring the StorageWorks shelf, note the following:
• Narrow SCSI (8-bit) devices can be used in the wide StorageWorks shelf, as
long as the devices are at a supported revision level. The narrow devices will
run in narrow mode.
• Narrow and wide devices can be mixed in the wide StorageWorks shelf. In a
mixed configuration, wide devices run in wide mode and narrow devices run
in narrow mode.
• For best performance, wide devices should be operated in wide SCSI-2 mode.
Supported devices and configuration rules for wide SCSI-2 are described in the
Wide SCSI Technical Bulletin. This bulletin is frequently updated and can be
downloaded from the Internet:
Via FTP on ftp.digital.com Once connected, go to /pub/Digital/ Alpha/systems
Via the World Wide Web at http://www.service.digital.com/alpha/server
Consult your controller documentation for other requirements.
5.8.2 External SCSI Expansion
External SCSI-2 devices, such as tabletop or rackmounted storage devices, can
be connected to the system using EISA- or PCI-based SCSI adapters. Use the
following rules to determine if a particular device can be used:
• The device must be supported by the operating system. Consult the software
product description for the device or contact the hardware vendor.
• A maximum of seven devices can be attached on any one SCSI-2 controller.
• Each device on the bus must have a unique SCSI ID. You may need to change
a device’s default SCSI ID in order to make it unique. All removable-media
device bus node IDs are set via switches on the device. For information about
setting a device’s ID, refer to the guide for that device.
• The entire SCSI bus length, from end-to-end, must not exceed 3 meters for
Fast SCSI-2 at 10 MB/sec (6 meters at 5 MB/sec).
• Ensure that the SCSI bus is properly terminated and that no devices in the
middle of the bus are terminated.
System Configuration and Setup 5–35
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