Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

Removing a host-to-virtual disk mapping using Linux DMMP

1. Unmount the file system containing the virtual disk.
   Using the following command: # umount filesystemDirectory
2. Run the following command to display multipathing topology:

   # multipath -ll

   NOTE: Use the multipath -ll command:

   • If a new LUN is mapped, the new LUN is detected and given a multipathing device node.
   • If you increased virtual disk capacity, the new capacity is displayed.

   NOTE: The virtual disk that you want to delete from the mapping. For example, the following information may be displayed:

   mpath6 (3600a0b80000fb6e50000000e487b02f5) dm-10

   DELL, MD32xx

   [size=1.6T][features=3 queue_if_no_path

   pg_init_retries 50][hwhandler=1 rdac]

   \_ round-robin 0 [prio=6][active]

   \_ 1:0:0:2 sdf 8:80 [active][ready]

   \_ round-robin 0 [prio=1][enabled]

   \_ 0:0:0:2 sde 8:64 [active][ghost]

   In this example, the mpath6 device contains two paths:

   -- /dev/sdf at Host 1, Channel 0, Target 0, LUN 2

   --/dev/sde at Host 0, Channel 0, Target 0, LUN 2

3. Flush the multipathing device mapping using the following command:

   # multipath -f /dev/mapper/mapth_x

   Where, mapth_x is the device you want to delete.
4. Delete the paths related with this device using the following command:

   # echo 1 > /sys/block/sd_x/device/delete

   Where, sd_x is the SD node (disk device) returned by the multipath command. Repeat this command for all paths related to this device. For example:

   #echo 1 > /sys/block/sdf/device/delete

   #echo 1 > /sys/block/sde/device/delete

5. Remove mapping from c, or delete the LUN if necessary.
6. If you want to map another LUN or increase virtual disk capacity, perform this action from MD Storage Manager.
   NOTE: If you are only testing LUN removal, you can stop at this step.
7. If a new LUN is mapped or virtual disk capacity is changed, run the following command: # rescan_dm_devs