SCSI Request Sense Key
Perhaps the most significant feature of the InveStore log file is its ability to capture the SCSI request sense key data that is reported by an storage device.
SCSI request sense key data is the internal data that the storage device itself reports to ASPI when it experiences hardware level error conditions. InveStore simply traps this data into the log file, for purposes of assisting in troubleshooting.
Using the tables found in the device manufacturer's SCSI command manual for that specific device, definitions are provided that can greatly aid in the resolution of a hardware problem.
The following is an example section of a log file that is displaying Request Sense Key data:
In the above-recorded instance, the log file is showing that the device at SCSI ID 02 (which in this case is an storage drive in a library) reported the SCSI Request Sense key of 04,09,02 during a "write with verify" operation to the target.
The first byte of the Sense Key information trapped in the log gives the general category for the error condition. In the above example Sense key 04 is for the general
category of a hardware error. The general categories that may be displayed in the log are:
The second and third bytes of information that are trapped in the log is the additional sense code and the additional sense code qualifier. These are device specific codes for a given storage library or drive.
Note: You must use the manufacturer’s SCSI command manual for that device to determine what the specific sense key indicates.
Using the tables in the device manufacturer’s SCSI command manual, the sense key 09,02 is a "focus servo failure". A "servo" (motor in the storage drive) failed the operation.
Now that the failure has been identified the troubleshooting efforts can now be focused on this drive. The drive can be placed offline or replaced, enabling a quicker transition back into a normal production environment.