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Section 4: SCSI Bridge Electronics
1.3
Front Panel LCD
A 4-line, 8-character-per-line, backlit liquid crystal display (LCD) provides you with performance
information, configuration selections, and diagnostic and special utility menus. During tape activity, the LCD
shows current tape-drive operation, a bar graph tracking tape capacity, and items such as total data transferred,
average transfer rate, compression ratio, ECC rate percentage, remaining tape capacity, and rewrite percentage.
When you enter the configuration, diagnostic, and utility menus, the LCD presents a series of items to choose
from and instructions to follow.
Write
E
TOTL XFR
74MB
Sample Performance Display
Figure 38
1.4
Understanding the Capacity Bar Graph
The capacity bar graph display updates dynamically during read and write operations. Beginning with the
native capacity of the cartridge (125m = 12.0 GB, 170m = 36.0 GB), as reported by the tape drive after a
cartridge is loaded. The SCSI bridge electronics applies the current average compression ratio (if any),
computes the then current maximum capacity, and displays the bar graph by incrementing or decrementing the
appropriate number of vertical bars between the empty icon and the full icon. There are thirty vertical bars,
each equating to approximately 3.33% of total capacity.
Empty Icon
Figure 39
2.1
Introduction
The SCSI bridge electronics are at the heart of the display system that provides performance information
about the tape operation. In addition to bridging communications between the host and tape drive, the
electronics autonomously send commands to the tape drive to extract the data necessary for the display. A
high-performance processor and dual SCSI buses allow the unit to appear to the host as a tape device on the
host bus, and to interface with the tape drive as a new host on the tape bus. This private tape bus can operate
independently of a host to provide such capabilities as code-tape generation, code-tape loading and off-line
HP StorageWorks DAT 72 (Models 5242 and 5242-ACL) User's Guide
SCSI ID:
[ 00 ]
F
PRESS to
Alter
Sample Configuration Display
Front panel LCD
Read
E
F
Full Icon
ECC Rate
0.0%
Capacity
Indicators
Understanding the capacity bar graph
Chapter Two
49
HP Part Number 528296-03 July 2005
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