Compaq 326817-003 manual Scsi Interface, Reliability of Backup Devices, Controller Requirements

Overview 1-3

The SCSI Interface

The Compaq 20/40 GB DAT 8-Cassette AutoLoader uses SCSI-2 as the interface to connect the host system.

IMPORTANT: In the information that follows, the term SCSI implies SCSI-2.

The SCSI implementation provides the DAT AutoLoader with a standard set of features and functions. These include the following:

■LVD Wide SCSI connection

■Synchronous data transfers

■Asynchronous data transfers

■Implementation of all mandatory and most optional commands of the Sequential Access command set

■Full implementation of mandatory Medium Changer commands

Controller Requirements

Compaq recommends equipping the computer with an LVD 32-bit Fast

SCSI-2 Controller or higher. Any of these controllers fully support the

Compaq 20/40 GB DAT 8 Cassette AutoLoader.

IMPORTANT: All SCSI devices on the same bus must either be internal (within the computer) or in an external storage device, but not both. The exception is a CD-ROM drive, which may be internal when other devices are external or vice versa.

Reliability of Backup Devices

The reliability of any backup device is directly related to its duty cycle (the number of hours per day that the device is in use). For example, if a tape drive designed for 24-GB backups is being used to back up a 100-GB computer, the result on that drive will be a need for accelerated preventive maintenance (especially head cleaning), premature aging, and reliability problems. See Chapter 5 for more information on cleaning requirements.