Access to SAN device failed with 'Add. Sense: Logical unit not supported' error messages

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux

Issue

  • Unable to access the SAN devices. The following errors are getting logged in /var/log/messages file while accessing the SAN devices:

      Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] CDB: Read(10): 28 00 00 00 00 80 00 00 08 00
  Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
  Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Sense Key : Illegal Request [current] 
  Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Add. Sense: Logical unit not supported
  Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] CDB: Read(10): 28 00 00 00 00 80 00 00 08 00
  Jun  5 11:33:41 host1 kernel: end_request: I/O error, dev sdbs, sector 16
  Jun  5 11:33:41 host1 kernel: end_request: I/O error, dev sdbs, sector 0
  [...]

Resolution

Please check with the SAN/Storage vendor to verify if the logical unit does not exist or is not mapped to the sender of the command or if there is any issue in the connectivity to affected SAN devices, due to which the READ SCSI command issued to SAN devices would be returning as failed. Are there any issues present from the FC switch, FC cabling, zoning or SAN/Storage array?

Root Cause

Following the error messages indicates that the driver had sent a READ SCSI command to sub path sdbs but the target device had responded to this command as Illegal Request because storage determined the logical unit does not exist or is not mapped to the sender of the command. The READ command is a very basic SCSI command which is used to read data from SCSI device, the failure in completion of READ command indicates that there is an issue on the SAN / Storage side due to which the target device is responding to READ command as Illegal Request.

    Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] CDB: Read(10): 28 00 00 00 00 80 00 00 08 00
    Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
    Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Sense Key : Illegal Request [current] 
    Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] Add. Sense: Logical unit not supported
    Jun  5 11:33:41 host1 kernel: sd 2:0:0:17: [sdbs] CDB: Read(10): 28 00 00 00 00 80 00 00 08 00
    Jun  5 11:33:41 host1 kernel: end_request: I/O error, dev sdbs, sector 16
    Jun  5 11:33:41 host1 kernel: end_request: I/O error, dev sdbs, sector 0
    [...]

The SCSI specification indicates a number of conditions under which storage will return an asc/ascq of 25h/00h:

ASC/ASCQ DZTPROMAEBKVF  Description
-------- -------------  ----------------------------------------------------
Content from www.t10.org is not included.25h/00h  DZTPROMAEBKVF  LOGICAL UNIT NOT SUPPORTED

For example:

if the logical unit reports a peripheral qualifier of 011b or 001b in its standard INQUIRY data (see 6.7.2), then return parameter data containing sense data with the sense key set to ILLEGAL REQUEST and the additional sense code shall be set to LOGICAL UNIT NOT SUPPORTED;

A peripheral qualifier of 011b and 001b are defined as:

Peripheral qualifier
=========================================================================================
Qualifier Description
001b      A peripheral device having the specified peripheral device type is not connected to this
          logical unit. However, the device server is capable of supporting the specified periph-
          eral device type on this logical unit.
011b      The device server is not capable of supporting a peripheral device on this logical unit.
          For this peripheral qualifier the peripheral device type shall be set to 1Fh. All other
          peripheral device type values are reserved for this peripheral qualifier.

So in this case, the lun the command was specified against is no longer present within storage, per the returned status.

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