ASC/ASCQ 5Dh and SMART disk drives

Elliott, Robert (Hou) Robert.Elliott at
Tue Jul 6 08:07:37 PDT 1999

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert (Hou)" <Robert.Elliott at>
ASC code 5Dh is used for Informational Exceptions.  Disk drives following
the "SMART" (non)standard use ASCQs from 10-7Fh to report detailed failure
prediction information.  However, SPC-2 Table C.1 only defines those ASCQs
for RBC devices.  RBC Table 18 defines the meaning of each code in that

How should we make these codes legal for SBC devices?  Ralph doesn't want
to just add SBC to the list of standards that use those codes, since it
doesn't define their meaning.  A reader wouldn't know to refer to RBC for
the definitions.  The codes are too disk-specific for SPC-2 itself.

If an SBC-2 project is started, it could certainly go there.  Gene noted
that the table could be added to the ISO version of SBC, since that is
still open.

SPC-2 revision 11 lists these ASC/ASCQ assignments in its annex 
(table C.1):
5D 00 Failure Prediction Threshold Exceeded (all devices)
5D 01 Media Failure Prediction Threshold Exceeded (MMC-2, RBC)
5D 02 Logical Unit Failure Prediction Threshold Exceeded (MMC-2)
5D FF Failure Prediction Threshold Exceeded (False) (all devices)
5D nn Detailed Failure Prediction Information (nn=10h-7Fh)(RBC)

RBC defines the ASCQs in this manner:
	Value		Meaning
upper nibble:  	
	0 		General Hard Drive Failure 
	1h 		Hardware impending failure
	2h		Controller impending failure
	3h		Data Channel impending failure
	4h		Servo impending failure
	5h		Spindle impending failure
	6h		Firmware impending failure
	7h	 	Reserved
	8h-Fh		Vendor-specific in SPC-2
lower nibble: 
     	0 		General Hard Drive Failure
     	1h		Drive Error threshold exceeding limits.
     	2h		Data Error Rate exceeding limits.
     	3h		Seek Error Rate exceeding limits.
     	4h		LBA reassignment exceeding limits.
     	5h		Access Times exceeding limits.  
     	6h		Start Unit Times exceeding limits.
     	7h		Channel parametrics indicate impending failure
     	8h		Controller detected impending failure.
    	9h		Throughput performance
	Ah		Seek time performance
	Bh		Spin-up retry count
	Ch		Drive calibration retry count
	Dh-Eh		Reserved.	

PC: Robert.Elliott at
UNIX: relliott at

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