zLinux zVM guests lost the paths to SAN disk with - 'Medium access timeout failure' errors

Issue

• When SAN storage got firmware upgraded, many zLinux zVM guests lost the paths to SAN disk with following errors:

  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: [sdg] Medium access timeout failure. Offlining disk!
  Jun  1 13:21:26 hostname kernel: sd 1:0:0:906: [sdh] Medium access timeout failure. Offlining disk!
  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: [sdg]  
  Jun  1 13:21:26 hostname kernel: sd 1:0:0:906: [sdh]  Result: hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK
  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: [sdg] CDB: Read(10): 28 00 0e 11 d7 58 00 00 18 00
  [...]
  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: rejecting I/O to offline device
  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: rejecting I/O to offline device
  Jun  1 13:21:26 hostname kernel: sd 0:0:0:906: [sdg]  Result: hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK
  [...]