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.
| 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 | |
| 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.