IBM T400F manual Cartridge Compatibility, Speed Matching and Channel Calibration, Sleep Mode

Cartridge Compatibility

The Ultrium 2 Tape Drive (Generation 2) uses the IBM TotalStorage LTO Ultrium 200 GB Data Cartridge and is compatible with the cartridges of its predecessor, the IBM Ultrium Internal Tape Drive (called Generation 1). The Ultrium 2 Tape Drive performs the following functions:

vReads and writes Generation 2 cartridges to Generation 2 format

vReads and writes Generation 1 cartridges to Generation 1 format

vDoes not write Generation 2 cartridges to Generation 1 format

vDoes not write Generation 1 cartridges to Generation 2 format

The Ultrium 2 Tape Drive reads tapes that have been written by other licensed Ultrium 2 drives. It also writes to tapes that can be read by other licensed Ultrium 2 drives.

In addition to using the IBM TotalStorage LTO Ultrium Data Cartridge with up to 200 GB capacity, the Ultrium 2 Tape Drive also offers read/write capability for certified LTO Ultrium tape cartridges.

Speed Matching and Channel Calibration

To improve system performance, the Ultrium 2 Tape 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 2 cartridge format to achieve a native data rate of 17.5, 21.9, 26.25, 30.63, or 35 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 which of the two data rates at which to operate. (For example, if the server transfers data at 60 MB/s on the host bus, at 2:1 compression its net data rate is 30 MB/s. The drive will then dynamically choose to operate at a native data rate of 26.25 or 30.63 MB/s, whichever enables it to successfully receive the greatest amount of compressed data over the network.) 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.

Sleep Mode

To conserve energy when circuit functions are not needed for drive operation, the Ultrium 2 Tape Drive features a power-management function that causes the drive’s electronics to enter a low-power mode known as sleep mode. To enter sleep mode, the drive must be inactive for a minimum of 15 minutes; to exit, the drive must receive a command across the SCSI or Fibre Channel interface, a command across the Library/Drive Interface (LDI or RS-422 interface), or a load or unload request. When in sleep mode, the drive’s response time to commands that do not require media motion increases by up to 10 microseconds. Commands that require media motion may be delayed an additional 100 milliseconds because the tape must be retensioned.

2IBM TotalStorage LTO Ultrium 2 Tape Drive