v
Does not write prior generation format to current generation cartridge.
The drive reads tapes that have been written by other licensed Ultrium 5 drives. It
also writes to tapes that can be read by other licensed Ultrium 5 drives.
In addition to using the IBM LTO Ultrium Data Cartridge with up to 1500 GB
capacity, the drive also offers read/write capability for certified LTO Ultrium tape
cartridges.
Speed Matching
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 different speeds when reading
or writing the Ultrium 4 or Ultrium 5 cartridge format. Native data rates are as
follows in the table below.
Table 1-2. Performance Parameters
Ultrium Generation Media
Generation 5 Media
Generation 4 Media
Generation 3 Media
Speed matching data
rates (MB/sec)
140.0
120.0
80.0
130.0
113.1
76.1
120.0
106.0
72.3
112.7
99.2
68.4
105.5
92.3
64.6
98.2
85.3
60.7
90.9
78.5
56.8
83.6
71.4
53.0
76.4
64.6
59.2
69.1
57.6
45.3
61.8
50.7
41.5
53.5
43.8
37.6
46.3
36.9
33.8
40.0
30.5
30.0
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.
Channel Calibration
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.
1-4
TS2250 Tape Drive Setup, Operator and Service manual
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