User`s guide

Chapter 3 Installing External Tape Drives
Reviewing Drive Default Settings
34 DDS-4/DAT 72 User’s Guide
SCSI ID 3 Each SCSI device on the bus must have its own unique ID. Your external
tape drive is shipped with a default SCSI ID of 6. If another SCSI device in
the SCSI chain is already using this ID, use the SCSI ID Selector switch on
the back of the drive to change the drive’s SCSI ID.
Figure 11 Back Panel
of the External Tape
Drive
Parity Checking 3 By default, parity checking is enabled on the external tape drive. If you
disable parity checking, the drive still generates a parity bit.
Data Compression3
By default, data compression is enabled. With this setting, the external
tape drive compresses all data written to tape and decompresses all
compressed data read from tape. The degree of compression varies due to
the type of data being processed.
• Data with a high degree of redundancy, such as structured database
files or graphics files, are compressed most efficiently, often at a ratio
of 2:1 or more.
• Data with little redundancy, such as executable programs, are
compressed the least.
Note: If you change the drive’s default SCSI ID, avoid using SCSI
IDs 0 and 1 (which typically are assigned to a boot drive) and
SCSI ID 7 (which typically is assigned to SCSI controllers or
host bus adapters. If you change the default SCSI ID, turn the
drive power off and back on.