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Media Type This field is ignored by the MODE SELECT command.
Buffered Mode Default = 1. The drive implements immediate reporting on WRITE
commands through its buffered mode. With Buffered Mode set to 1,
the drive reports GOOD status on WRITE commands as soon as the
data block has been transferred to the buffer. If this field = 0, then
the drive does not report GOOD status on WRITE commands until
the data blocks have been written to tape.
When Buffered Mode is not used, the tape drive suffers significant
performance degradation, and possible capacity, depending on tape
format, block size, and compression. When using the 10 or 20 GB
format with compression disabled and block size a multiple of 8
Kbytes, there is no capacity loss.
When writing 10 , 15,20, or 40 GB format with compression enabled
and Buffered Mode disabled, some capacity loss can occur. The
block packing feature is essentially disabled by turning off Buffered
Mode.
If Buffered Mode is set to a number greater than 1, the command is
rejected with CHECK CONDITION, sense key of ILLEGAL
REQUEST.
Speed The value of this field specifies the speed at which the drive will
match the transfer rate of the host.
The default setting = 0. Tape system will attempt to match the
drive’s throughput with the host data throughput.
1 = Used for systems with bus speed below 5.0MB/second.
2 = Used for systems with bus speeds between 5.0 and
6.0MB/second
3 = Used for systems with bus speeds of 6.0MB/second or greater.
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Block Descriptor
Length This field specifies the length in bytes of all the block descriptors.
Since the drive only allows one block description, the value must be
either 0 or 8. A value of 0 indicates no block description is included;
a value of 8 indicates a block descriptor is present and precedes the
mode page data. Any other value other than 0 or 8 causes a
CHECK CONDITION status with sense key of ILLEGAL REQUEST
to be returned.
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