VirtualWisdom Health - SCSI Timeout & decoding SCSI Status Codes

SCSI Timeout

The SCSI Timeout value is server side configurable parameter. It is typically between 5 to 60 seconds.

The Operating System’s SCSI Layer sets a timer on each SCSI command. When this timer expires, the SCSI layer will quiesce the host bus adapter (HBA) and wait for all outstanding commands to either time out or complete.

Most commonly, Timeouts occur in one of the following conditions:

  • A SCSI Command is timed out and aborted
  • A SCSI device reset is attempted
  • A SCSI bus reset is attempted. This may have an adverse effect on other devices sharing that SCSI bus.
  • A SCSI host (bus adapter) reset is attempted. This is an attempt to re-initialize the adapter card associated with the SCSI device that has the timed out command.

What is a SCSI Status code?

A SCSI Status Code is used to determine the success or failure of an individual SCSI command. At the end of any command, the target returns a Status Code byte which should be one of the following:

00h GOOD

02h CHECK CONDITION

04h CONDITION MET

08h BUSY

18h RESERVATION CONFLICT

28h TASK SET FULL

30h ACA ACTIVE

40h TASK ABORTED

List Of Check Condition SCSI Status Codes

When the target returns a Check Condition in response to a command it is indicating that it has entered a contingent allegiance condition. This means that an error occurred when it attempted to execute a SCSI command. In FCP the Key Code Qualifier (KCQ) from the target is included in the response.

To translate from Virtual Wisdom, Status is the SCSI Status Code, Sense is the Key (or Sense Key), and Additional Sense is the ASC/ASCQ (Additional Sense Code/Additional Sense Code Qualifier) combination to provide the details of the check condition.

To interpret each SCSI Status code, see http://www.t10.org/lists/2status.htm

Steps to interpret SCSI Status Code

Step1: Check the SCSI Status Code : http://www.t10.org/lists/2status.htm

Step2: Check the SCSI Sense Key : http://www.t10.org/lists/2sensekey.htm

Step3: Determine ASC (Additional Sense Code) and ASCQ (Additional Sense Code Qualifier) http://www.t10.org/lists/asc-num.htm