The Scsi Interface; Controller Requirements; Reliability Of Backup Devices - Compaq DAT AutoLoader Reference Manual

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:
I
LVD Wide SCSI connection
I
Synchronous data transfers
I
Asynchronous data transfers
I
Implementation of all mandatory and most optional commands of the
Sequential Access command set
I
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.
Overview 1-3