IBM 25R0012 User Guide - Page 19

Panel, Drive, Speed, Matching, Channel, Calibration

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Rear Panel of the SCSI Drive 1 SCSI connector 4 2 SCSI ID connector 5 3 Power connector Library/Drive Interface (LDI or RS-422 interface) connector Serial port 4 a82ru011 1 Figure 3. Rear panel of the drive 2 3 5 Speed Matching and Channel Calibration To improve system performance, the drive uses a technique called speed matching to dynamically adjust its native (uncompressed) data rate to the slower data rate of a server. With speed matching, the drive operates at one of five speeds when reading or writing the Generation 3 cartridge format to achieve a native data rate of 40, 50, 60, 70, or 80 MB per second (MB/s). If the server's net (compressed) data rate is between two of the preceding native data rates, the drive calculates the appropriate data rate at which to operate. Speed matching dramatically reduces backhitch, the condition that occurs when a tape stops, reverses, and restarts motion. A backhitch is usually the result of a mismatch between the data rates of the server and the drive. System performance is further optimized by a feature called channel calibration, in which the drive automatically customizes each read/write data channel to compensate for variations in such things as the recording channel's transfer function, the media, and characteristics of the drive head. Product Description 3

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Rear
Panel
of
the
SCSI
Drive
±1²
SCSI
connector
±4²
Library/Drive
Interface
(LDI
or
RS-422
interface)
connector
±2²
SCSI
ID
connector
±5²
Serial
port
±3²
Power
connector
Speed
Matching
and
Channel
Calibration
To
improve
system
performance,
the
drive
uses
a
technique
called
speed
matching
to
dynamically
adjust
its
native
(uncompressed)
data
rate
to
the
slower
data
rate
of
a
server.
With
speed
matching,
the
drive
operates
at
one
of
five
speeds
when
reading
or
writing
the
Generation
3
cartridge
format
to
achieve
a
native
data
rate
of
40,
50,
60,
70,
or
80
MB
per
second
(MB/s).
If
the
server’s
net
(compressed)
data
rate
is
between
two
of
the
preceding
native
data
rates,
the
drive
calculates
the
appropriate
data
rate
at
which
to
operate.
Speed
matching
dramatically
reduces
backhitch,
the
condition
that
occurs
when
a
tape
stops,
reverses,
and
restarts
motion.
A
backhitch
is
usually
the
result
of
a
mismatch
between
the
data
rates
of
the
server
and
the
drive.
System
performance
is
further
optimized
by
a
feature
called
channel
calibration
,
in
which
the
drive
automatically
customizes
each
read/write
data
channel
to
compensate
for
variations
in
such
things
as
the
recording
channel’s
transfer
function,
the
media,
and
characteristics
of
the
drive
head.
5
1
2
3
4
a82ru01
1
Figure
3.
Rear
panel
of
the
drive
Product
Description
3