Quantum DLT 4000 Manual descarregar pdf (Página 165)

SCSI Commands

Quantum DLT 4000 Tape Drive 5-65

MODE SELECT (6) / (10) Command (15h) / (55h) (continued)

Table 5–34 MODE SELECT Mode Parameter Header - Field Descriptions

Field Name Description

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 writing 2.6 or 6.0 GB formats

and block size that is a multiple of 4 Kbytes, there is no capacity loss.

Likewise, 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 or 20 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 tape drive supports only its default speed.

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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Quantum DLT 4000 Manual Página 165