HGST Ultrastar 7K4000 (SAS) Hard Disk Drive Specification
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18.36 REQUEST SENSE (03)
Table 189: REQUEST SENSE (03)
The REQUEST SENSE command requests the drive to transfer sense data.
The Descriptor Format (DESC) bit specifies which sense data format the device shall return in the parameter data. The
Allocation Length specifies the maximum number of bytes of sense data that the drive should return. Such relationship is shown
in the table below. (See 22.0, SCSI Sense Data for more details).
Table 190: Sense Data Format and Length
If REQUEST SENSE command with an invalid LUN is received, the drive returns Good status and reports a sense key of Ille-
gal Request and an additional sense code of Logical Unit Not Supported.
If the drive has no sense data available to return, it will return a sense key of No Sense and an additional sense code of No
Additional Sense Information.
Separate sense data is maintained by the device for each Initiator. Therefore, there is no requirement for an Initiator to expedi-
tiously clear a Check Condition as this will not affect other initiators in a multi-Initiator system.
Byte
Bit
76543210
0 Command Code = 03h
1 Reserved = 0 DESC
2-3 Reserved = 0
4 Allocation Length
5 VU = 0 Reserved = 0 FLAG LINK
DESC Bit Sense Data Format Length of Sense Data Returned
0b Fixed format The number of bytes in the Allocation Length or 32 bytes, whichever is less
1b Descriptor format
The number of bytes in the Allocation Length or a fixed "descriptor sense
data size", whichever is less. The "descriptor sense data size" is either 40 or
60 bytes, depending on the drive firmware build.
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