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Cartridge Compatibility
Speed Matching
Channel Calibration
Sleep Mode
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The drive (Generation 3) uses the IBM TotalStorage LTO Ultrium 400 GB Data
Cartridge and is compatible with the cartridges of its predecessor, the IBM Ultrium
Internal Tape Drive (Generation 2). The drive performs the following functions:
v Reads and writes Generation 3 cartridges to Generation 3 format
v Reads and writes Generation 2 cartridges to Generation 2 format
v Reads Generation 1 cartridges
v Does not write Generation 3 cartridges to Generation 2 format
v Does not write Generation 2 cartridges to Generation 3 format
v Does not write Generation 1 cartridges
The drive reads tapes that have been written by other licensed Ultrium 3 drives. It
also writes to tapes that can be read by other licensed Ultrium 3 drives.
In addition to using the IBM TotalStorage LTO Ultrium Data Cartridge with up to
400 GB capacity, the drive also offers read/write capability for certified LTO
Ultrium tape cartridges.
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.
To conserve energy when circuit functions are not needed for drive operation, the
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 30 seconds (default value; this is programmable via
the mode pages); 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
ten microseconds. Commands that require media motion may be delayed an
additional 100 milliseconds because the tape must be retensioned.
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