HP NonStop G-Series - Manual (Page 22)

Chapter Five - SCSI Bridge Electronics
The average compression/decompression ratio appears as the ratio of the compressed and
uncompressed data lengths reported by the tape drive. The ratio always appears in the format
X.X:X
.
5.7.5 Remaining Capacity
This value is an estimate of remaining tape capacity. It is computed by multiplying the average
compression ratio by the remaining block count.
KB
,
MB,
and
GB
represent multipliers of
1024, 1024 x 1024, and 1024 x 1024 x 1024, respectively.
Read
E F
REMAIN'G
1.7GB
Figure 21 Remaining capacity readout
5.7.6 ECC/Rewrite
Percentage
The number of ECC (when reading) or rewrite (when writing) occurrences, as a percentage of the
total number of read or write commands since the last rewind, appears in the format
XX.X
. In
general, error rates are the highest at the beginning of a tape because this part of the tape is written
to every time the tape unloads. When this area becomes worn, tapes become unreliable. Errors
above 10.0 suggest worn tapes or the need to clean the recording heads.
Read
E F
RWr RATE
0.0%
Read
E F
ECC Rate
0.0%
Figure 22 ECC/Rewrite percentage displays
5.8
Setting Tape Density
Tape density format can be controlled by the SCSI bridge electronics or by the NonStop server. Some
applications do not function without having software control. When the appropriate drivers exist, the latter
method is preferred, and a setting of
FF
(default setting) should be used. When the unit is not busy, you
can change the tape density by pressing the mode switch. Pressing the mode switch cycles the available
density settings. The options for tape density appear on the LCD.
CO = compression on
DEN=CO
Rev 0096
5170
T134 ID5
40 = compression off
DEN=40
Rev 0096
5170
T134 ID5
Valve should be
at FF only
DEN=FF
Rev 0096
5170
T134 ID5
Figure 23
Compression selection screens
HP StorageWorks DAT 72 (Model 5242-2SE) User's Guide
18 HP Part Number 528297-003 July 2005