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C141-E235 7-1
CHAPTER 7 Error Analysis
7.1 Error Analysis Information Collection
7.2 Sense Data Analysis
This chapter explains in detail how sense data collected from a disk drive is used for troubleshooting. Sense
data reflects an error in the disk drive, and helps with troubleshooting.
A sense key, additional sense code, and additional sense code qualifier, taken from various sense data are
repeated. Also in this chapter, troubleshooting is performed using these three codes. Unless otherwise
specified, "sense data" means the above three codes. When sense data is represented as (x-xx-xx), the
leftmost x is a sense key, the middle xx is an additional sense code, and the rightmost x is an additional sense
code qualifier.
7.1 Error Analysis Information Collection
7.1.1 Sense data
When the HDD posts a CHECK CONDITION status or detects a fatal error in the loop, the current
command or queued command is cleared. In such a case, the HDD generates sense data about the
command-issuing initiator. The initiator can read the sense data by issuing a REQUEST SENSE
command.
Even if a transfer byte length that is shorter than the sense data length of the tested device is
specified, the command terminates normally. In this case, however, the initiator receives part of the
sense data, but the remaining part of the sense data is lost.
For details of the REQUEST SENSE command, refer to Subsection 4.1.14 “REQUEST SENSE
(15)” of the Fibre Channel Interface Specifications.
7.1.2 Sense key, additional sense code, and additional sense code qualifier
If an error is detected in a disk drive, the error status is indicated in the sense data collected from the
disk drive. Figure 7.1 shows the positions of a sense key, additional sense code, and additional sense
code qualifier.