Section 4: SCSI Bridge Electronics
Write
E F
XFR RATE
425KB/s
Figure 45
Transfer rate LCD
Note
: Tape drives incorporate a data buffer to help maintain a constant data rate to the recording
heads. When this buffer is empty, 1 MB of data or more can appear to be instantly written
to the tape drive and a correspondingly high transfer rate is displayed on the LCD. When
the buffer is sufficiently full, the recording heads are set in motion.
A substantial delay accompanies the first write operation to tape. This results in a drop in
the transfer rate. With continued writing to the tape drive, the tape constantly moves and the
average transfer rate approaches the quoted streaming rate.
2.3.4 Compression
Ratio
Write
E F
COMPRESS
2.3:1
Figure 46
Compression ratio LCD
The average compression/decompression ratio shows as the ratio of the compressed and
uncompressed data lengths as reported by the tape drive. The ratio always appears in the format
XX:X
.
2.3.5 Remaining
Capacity
This value is an estimate of remaining tape capacity that is computed by multiplying the average
compression ratio by the remaining block count, which was obtained from the tape drive.
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 47
Remaining capacity readout
2.3.6 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, appear 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.
HP StorageWorks DAT 72 (Models 5242 and 5242-ACL) User's Guide
52 HP Part Number 528296-03 July 2005
