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sense data
sequential access
single-ended
spacing
sub-data set
synchronous
TapeAlert
vendor-unique
168 glossary
Ultra2 SCSI can transfer data at up to 80 MB/s wide, using a cable of up to
25 meters total length for a single device, or up to 12 meters for two or more
devices (it is also known as "Fast40").
Ultra3 or Ultra160 can transfer data at up to 160 MB/s wide. Cable lengths
are as for Ultra2.
Ultra4 or Ultra320 will transfer at up to 320 MB/s.
Ultra SCSI supports both SE and LVD interfaces. In normal situations, slower
devices can coexist with faster devices, and narrow devices can be used on the
same SCSI bus as wide devices using a suitable adapter.
HP's Generation 1 Ultrium drives are Ultra2, wide SCSI-3 compatible devices.
They can be used with both LVD and SE host bus adapters.
Generation 2 Ultrium drives are Ultra160, wide SCSI-3 compatible.
Data returned after the execution of a SCSI command, telling the host whether
the transaction was successful, and if not, what went wrong.
Sequential access devices store data sequentially in the order in which it is
received. Tape devices are the most common sequential access devices.
Devices such as disk drives are direct access devices, where data is stored in
blocks, not necessarily sequentially. Direct access allows for speed of retrieval,
but is significantly more costly.
see
SCSI
Spacing is moving along the tape over a specified number of blocks or
filemarks, or to EOD, in order to find data quickly.
One sixteenth of a
data set
see
data transfer phase
A set of 64 flags is held in the TapeAlert log that indicate faults or predicted
faults with the drive or the media. By reading this log, host software can inform
the user of existing or impending conditions, and can, for example, advise the
user to change the tape.
The addition of commands to SCSI that are not included in the standard.
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