The RAO implementation in LTO produces the best results for performance enhancement when there is little variability in block size or data compression ratio. When the
variability in compression ratio or block sizes increase, the accuracy of the locate estimates may be reduced and any potential performance enhancements may be
diminished.
Archive mode unthread
The drive archive mode unthread feature is designed to fine-tune the media for long term storage by ensuring that the media inside the cartridge is stored at an optimal
tension.
Tuning to optimal tension requires longer unthread time. The time that is required for an unload depends on how the cartridge has been used during the mount. This is
based on the current position and how far from the beginning of tape (BOT) the media has been moved since mount. For details on unload performance, see
This feature is available with LTO-7 and later tape drives. For more details, see
Speed matching
To improve system performance, the drive uses a technique that is 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 it is reading or writing the Ultrium 7 or later cartridge format. Native data rates are shown in the table.
Table 1. Performance parameters for full height drives
Ultrium Generation Media
Generation 9 media Generation 8 media Generation 7 media
Speed matching data rates (MB/sec) 408
365.0
306.0
385
341.0
287.52
366
318.0
268.56
347
306.4
250.66
325
273.0
231.86
305
249.5
213.06
284
226.0
194.26
263
203.0
175.46
244
180.0
157.67
223
157.5
138.52
203
135.0
120.11
177
112.0
101.46
Table 2. Performance parameters for half height drives
Ultrium Generation Media
Generation 9 media Generation 8 media Generation 7 media
Speed matching data rates (MB/sec) 284
306.4
306.0
263
273.0
287.52
244
249.5
268.56
223
226.0
250.66
203
203.0
231.86
177
180.0
213.06
-
157.5
194.26
-
135.0
175.46
-
112.0
157.67
-
-
138.52
-
-
120.11
-
-
101.46
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 optimized by channel calibration.
System performance is further optimized by a feature that is 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.
86
IBM TS22xx - TS2290, TS2280, and TS2270
