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How to decode STIO: found hung cmd

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Applies to

  • ONTAP 9 and Later
  • ONTAP 8.3.x
  • ONTAP 8.2 7-Mode

Answer

  • STIO (SCSITarget I/O) messages are SCSI protocol level errors that are used to help, interpret, and diagnose the root cause for SCSI related issues.
  • When a FC target adapter encounters a SCSI command error during its processing, its logged in the EMS/messages.
  • STIO messages have different meanings and can be decoded based upon the 'STATE' of the check condition during which the command is hung.

Example from EMS logs

STATE 5 : Mon Apr 18 00:37:03 EDT [controller1: fct_tpd_thread_6: fcp.io.status:debug]: STIO Adapter:0a, found hung cmd:0xffffff0200ef83a0(state=5, flags=0x0, ctio_sent=1/1,RecvExAddr=0x127524, OX_ID=0x43xx, RX_ID=0xffff,SID=0x10axx, Cmd[2A])

STATE 8: Tue Aug 16 11:33:01 MST [controller2: fct_tpd_thread_2: fcp.io.status:debug]: STIO Adapter:0f, found hung cmd:0xffffff02023592b0(state=8, flags=0x1, ctio_sent=0/1,RecvExAddr=0x1222b0, OX_ID=0x5dxx, RX_ID=0xffff,SID=0x400xx, Cmd[88])

As mentioned above, each state has a different meaning and can be decoded with the below table.

State:  Reason
1 FREE
2 PREPROCESS
3 SCSITCB_WAIT
4 DATAIN_SENT 
5 DATAOUT_WAIT 
6 DATAOUT_RCVD,STIO
7 RESP_SENT 
8 DATAINRESP_SENT 
9 DATAINRESP_CMPL 
10 TERMINATE_WAIT 
11 SCSITMF_WAIT 
12 LAST
13 t

The table above can be used to diagnose where through FC target command processes the issue occurred.

For example, adding a little context to each state:

state=5: DATAOUT_WAIT  This indicates that the FC target is waiting for something to come back from the host after accepting the write request; however, nothing came back within the expected timeout value.

state=8: DATAINRESP_SENT  This indicates that the FC target is waiting for something to come back from the host after accepting the read request; however, no payload was received within the expected timeout value.

Additional Information

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