Symptoms

VMkernel logs are flooded with the following error: WARNING: lpfc: lpfc_handle_fcp_rsp_err:4915: 0:(0):2757 Protocol failure detected during processing of FCP I/O op: tgt x2 lun x1 cmnd x28 rspInfo3 x2 2021-11-08T14:22:08.949Z cpu8:2098569)WARNING: lpfc: lpfc_handle_fcp_rsp_err:4939: 1:(0):2757 Protocol failure detected during processing of FCP I/O op: tgt x1 lun x0 cmnd x28 rspInfo3 x2 ** The read commands are rejected by Unity Array with RSP_CODE=0x2 indicating "FCP_CMND fields invalid"** The failure in read commands results in path going DEAD/FlappingSevere performance issue is reported.

Cause

Unity storage array does not properly handle nonzero value in reserved field (COMMAND REFERENCE NUMBER - Byte8) of FCP command. When the FCP_CMND payload byte 8 (COMMAND_REFERENCE_NUMBER) is not zero, Unity rejects the command with an FCP_RSP_CODE of 2, INVALID_FIELD.Based on FCP 4 / 5 specifications, the target array should ignore that field if it does not support it.

Resolution

Unity OE 5.2.0.0.5.173 contains the fix for this issue.

Support Cases