문제

  • Unable to remove the multipath device after unmapping the LUN from the server.

  • Attempting to flush a multipath map with "multipath -f" or "multipath -F" results in "map in use":

    Raw
         # multipath -f mpath7
     mpath7: map in use

  • The multipath command still shows the multipath device, with path(s) to the unmapped LUN as follows:

    Raw
         # multipath -ll mpath7
     mpath7 (36090a01870982994dcb8d4405ed03cbf) dm-7 ,
     [size=4.4T][features=1 queue_if_no_path][hwhandler=0][rw]
     \_ round-robin 0 [prio=0][enabled]
     \_ #:#:#:# -   #:#   [failed][faulty]

환경

  • Red Hat Enterprise Linux 5, 6
  • Device mapper multipath
  • SAN connected storage

해결

  • Locate any subsystem or process holding the multipath device open.  See diagnostic steps for possible tools and techniques.
  • For any subsystem or process holding the multipath device open, stop the process, or issue commands to release the multipath device.

  • Some examples of possible holders of a multipath device and the commands to release it:

    1. A filesystem exists on the multipath device and is currently mounted.
      • Unmount the filesystem and if it exists in /etc/fstab, remove it.
    2. One or more partition mapping(s) still exists on the multipath device.
      • Use "kpartx -d" on the multipath device to remove the device partition mapping(s).
    3. The multipath device was used by LVM, and still has device mapper state in the kernel.
    • Use "lvchange -an" to deactivate any logical volume(s) associated with the multipath device.  A list of logical volumes associated with the multipath device may be found by examining the output of "lvs -o +devices".
    • If "lvchange -an" fails, the logical volume is only partially removed, or there are blocked processes with I/O outstanding on the device, use "dmsetup remove -f" followed by "dmsetup clear" on the multipath device.  See dmsetup man page for full explanation of these commands.

  • Once all holders of the device have been removed, the multipath device should be flushed with "multipath -f".

근본 원인

  • The multipath device was held open by at least one process or subsystem.

진단 단계

  • Use 'lsof' to attempt to find anyone holding the device open.
  • Check 'dmsetup' output for any device mapper maps that depend on the multipath device
  • Check the if there is a device for mpath7 in /dev/mapper/mpath7
  • Check multipath -v4 -ll

 

* 실제 필드에서 작업하면서 느끼는 것은.. 그렇다라도 스토리지 변경작업은 서버 리부팅을 권장한다.