Different behavior in RHEL6 and in RHEL7 when storage controller was brought down for maintenance.

Issue

• RHEL 6 nodes failed all paths to the storage where as RHEL 7 nodes failed only relevant paths when storage controller was brought down for maintenance.
• After one of the controllers was brought down for maintenance, only RHEL6 nodes with DM Multipath lost all the paths to the storage whereas RHEL7 nodes lost only paths through the problematic controller. Paths through other storage controller were available in RHEL7 but not in RHEL6.
  RHEL7 logs

Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:5: [sdy] tag#20 FAILED Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:5: [sdy] tag#20 CDB: Test Unit Ready 00 00 00 00 00 00
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:11: [sdae] tag#12 FAILED Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:11: [sdae] tag#12 CDB: Test Unit Ready 00 00 00 00 00 00
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:15: [sdai] tag#24 FAILED Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:15: [sdai] tag#24 CDB: Test Unit Ready 00 00 00 00 00 00
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:16: [sdaj] tag#17 FAILED Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:16: [sdaj] tag#17 CDB: Test Unit Ready 00 00 00 00 00 00
Feb  5 04:32:21 rhel7-node kernel: sd 1:0:1:9: [sdac] tag#2 FAILED Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK

RHEL 6 logs

Feb  5 04:31:40 rhel6-node multipathd: mpathdk: sdcp - tur checker timed out
Feb  5 04:31:40 rhel6-node multipathd: checker failed path 69:208 in map mpathdk
Feb  5 04:31:40 rhel6-node multipathd: mpathdk: remaining active paths: 3
Feb  5 04:31:40 rhel6-node kernel: device-mapper: multipath: Failing path 69:208.
Feb  5 04:31:40 rhel6-node multipathd: mpathch: sdcu - tur checker timed out
Feb  5 04:31:40 rhel6-node multipathd: checker failed path 70:32 in map mpathch
Feb  5 04:31:40 rhel6-node multipathd: mpathch: remaining active paths: 3
Feb  5 04:31:40 rhel6-node multipathd: mpathfh: sdct - tur checker timed out
Feb  5 04:31:40 rhel6-node multipathd: checker failed path 70:16 in map mpathfh
Feb  5 04:31:40 rhel6-node multipathd: mpathfh: remaining active paths: 3
Feb  5 04:31:40 rhel6-node multipathd: mpathcl: sdcv - tur checker timed out
Feb  5 04:31:40 rhel6-node multipathd: checker failed path 70:48 in map mpathcl