HP NonStop G-Series - Manual (Page 21)

Chapter Five - SCSI Bridge Electronics
Total data bytes read from or written to the unit appear with a
KB
(1024),
MB
(1024 x 1024) or
GB
(1024 x 1024 x 1024) multiplier. On the first read or write command following a rewind, the count
is set to zero.
Write
E F
TOTL XFR
74MB
Figure 18 Total data transferred LCD
5.7.3
Transfer Rates in KiloBytes per Second
The average transfer rate between the host and the unit is calculated by dividing the total data
transferred by the elapsed time since the first read or write command after a rewind or write
filemark.
Write
E F
XFR RATE
425KB/s
Figure 19 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, 8 MB of data or more can appear to be instantly written
to the tape drive, and a correspondingly high transfer rate occurs. When the buffer is
sufficiently full, the recording heads are set in motion.
A substantial delay accompanies this first write-to-tape (much like the delay you experience
after pressing the play button of a VCR). This delay results in a drop in the transfer rate.
With continued writing to the unit, the tape constantly moves and the average transfer rate
approaches the quoted streaming rate.
5.7.4 Compression
Ratio
Write
E F
COMPRESS
2.3:1
Figure 20 Compression ratio LCD
HP StorageWorks DAT 72 (Model 5242-2SE) User's Guide
17 HP Part Number 528297-003 July 2005