How to Troubleshoot Hard Drive Sense Errors on a Dell PowerEdge™ Server

Issue 1: Key Code Qualifier

When a SCSI target device returns a check condition in response to a command, the initiator then issues a SCSI Request Sense command. This process is part of a SCSI protocol called Contingent Allegiance Condition. The target responds to the Request Sense command with a set of SCSI sense data which includes three fields giving increasing levels of detail about the error:

• K - sense key - 4 bits, (byte 2 of Fixed sense data format)
• C - additional sense code (ASC) - 8 bits, (byte 12 of Fixed sense data format
• Q - additional sense code qualifier (ASCQ) - 8 bits, (byte 13 of Fixed sense data format)

The initiator can take action based on just the K field which indicates if the error is minor or major. However all three fields are logically combined into a 20-bit field called Key Code Qualifier or KCQ. The specification for the target device defines the list of possible KCQ values. In practice, there are many KCQ values which are common between different SCSI device types and different SCSI device vendors.

For more information and a list of common Key Code Qualifiers, click (here ). 

For a listing of SCSI ASC/ASCQ Assignments, click (here).

• K - sense key - 4 bits, (byte 2 of Fixed sense data format)
• C - additional sense code (ASC) - 8 bits, (byte 12 of Fixed sense data format
• Q - additional sense code qualifier (ASCQ) - 8 bits, (byte 13 of Fixed sense data format)

The initiator can take action based on just the K field which indicates if the error is minor or major. However all three fields are logically combined into a 20-bit field called Key Code Qualifier or KCQ. The specification for the target device defines the list of possible KCQ values. In practice, there are many KCQ values which are common between different SCSI device types and different SCSI device vendors.

For more information and a list of common Key Code Qualifiers, click (here). 

For a listing of SCSI ASC/ASCQ Assignments, click (here).

Issue 2: Sense Code 5D Reported

• Have a backup in place as the disk can fail at any time. The risks are mitigated by the appropriate RAID level.
• Replace the disk under warranty or contact Dell and buy a replacement disk if out of warranty.
• If there are any updates available for the remaining disk models in the RAID subsystem, then upgrade these to help improve reliability and avoid future failures. RAID controller firmware, operating system device drivers and monitoring software such as OpenManage Server Administrator (OMSA) can also be updated.