Common Features; Configuring The Enclosure Scsi Bus - Compaq 4200 User Manual

3–2 Compaq StorageWorks Enclosure 4200 Family LVD Disk Enclosure User Guide

Common Features

The following features are common to both the single- and the dual-bus I/O modules.
These modules are pluggable elements. Replacing either I/O modules or the cables
requires stopping all data transfers to prevent the loss of data.
Each enclosure requires an I/O module for operation with a wide (16-bit) Ultra2 LVD
SCSI controller. The module is the CRU that connects the enclosure to the host controller
through a 68-pin, VHDCI connector and a SCSI bus cable. This module can support a
maximum of 14 drives in a single enclosure or on a single-bus.
Each enclosure has two SCSI buses. Half of the drive bays are on each bus. The I/O
module type (single- or dual-bus) determines the enclosure bus configuration.
When using the single-bus I/O module with all the addressable devices on the same
bus (SCSI bus A). This configuration requires one controller or host adapter.
When using the dual-bus I/O module half the addressable devices are on SCSI bus A
and the other half are on SCSI Bus B. This configuration requires two controllers or
host adapters.
See "Single-Bus SCSI Address Maps" and "Dual-Bus SCSI Address Maps" for
information about the drive SCSI bus addresses.

Configuring the Enclosure SCSI Bus

Installing an I/O module automatically configures the enclosure for either single- or
dual-bus operation. Such installation automatically changes the drive SCSI bus IDs.
CAUTION: To prevent the loss of data it is necessary to stop all data transfers when
connecting or disconnecting a SCSI bus cable or removing and installing an I/O
module.
CAUTION: To avoid the possibility of losing data, always backup data before installing
a different type I/O module.