Issue

• How to set custom max_sectors_kb option for multipath devices and its sub paths without causing any disruption to ongoing IO operations?

• While changing the max_sectors_kb option for multipath devices and its sub paths with following command, the IO operations started to fail with below errors:

  $ echo '256' > /sys/block/<device>/queue/max_sectors_kb 
  
  $ tail -f /var/log/messages
  kernel: blk_cloned_rq_check_limits: over max size limit.
  kernel: blk_cloned_rq_check_limits: over max size limit.
  kernel: blk_cloned_rq_check_limits: over max size limit.
  kernel: device-mapper: multipath: Failing path 70:61.
  kernel: device-mapper: multipath: Failing path 71:81.
  multipathd: 70:61: mark as failed
  multipathd: crs_01: remaining active paths: 1
  multipathd: 71:81: mark as failed
  [...]
  

  • The same issue was not observed with kernel versions older than 2.6.32-642.el6 and 3.10.0-327.el7.