Quantum DLT 4000 Product Manual page 208

DLT4000 SCSI Interface
compression. If writing 2.6 or 6.0 GByte formats, if the block size is a multiple of 4
Kbytes, there is no capacity loss. When using the 10 GByte or 20 GByte format, if
compression is disabled and the block size is a multiple of 8 Kbytes, there is no
capacity loss.
When using the 10/20 GByte format and compression enabled, not having buffered
mode enabled will cause some capacity loss, depending on compression ratios. This is
because the block packing feature is essentially disabled by turning off buffered mode.
If this field is greater than 1, the command will be rejected with a Check Condition,
with a Sense Key of ILLEGAL REQUEST.
Speed
The tape drive supports only one speed, the default speed.
Block Descriptor Length
This specifies the length in bytes of all the block descriptors. Since the drive only
allows one block descriptor, this value must be 8 or 0. Any other value causes a
CHECK CONDITION status with an ILLEGAL REQUEST sense key to be returned.
8-48 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem