Dell POWERVAULT MD3600I - Manual (Page 89)

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 multi-pathing 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 volume 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 volume capacity is changed, run the following command: # rescan_dm_devs
Restricted Mappings
Many hosts are able to map up to 256 LUNs (0 to 255) per storage partition. However, the maximum number of mappings
differs because of operating system variables, failover driver issues, and potential data problems. The hosts listed in the
table have these mapping restrictions.
If you try to map a virtual disk to a LUN that exceeds the restriction on these operating systems, the host is unable to
access the virtual disk.
Operating System Highest LUN
Windows Server 2003 and Windows Server 2008 255
Linux 255
Guidelines when you work with host types with LUN mapping restrictions:
• You cannot change a host adapter port to a restricted host type if there are already mappings in the storage
partition that would exceed the limit imposed by the restricted host type.
• Consider the case of the Default Group that has access to LUNs up to 256 (0 to 255) and a restricted host type is
added to the Default Group. In this case, the host that is associated with the restricted host type is able to
access virtual disks in the Default Group with LUNs within its limits. For example, if the Default Group had two
virtual disks mapped to LUNs 254 and 255, the host with the restricted host type would not be able to access
those two virtual disks.
• If the Default Group has a restricted host type assigned and the storage partitions are disabled, you can map
only a total of 32 LUNs. Any additional virtual disks that are created are put in the Unidentified Mappings area. If
additional mappings are defined for one of these Unidentified Mappings, the Define Additional Mapping dialog
shows the LUN list, and the Add button is unavailable.
• Do not configure dual mappings on a Windows host.
• If there is a host with a restricted host type that is part of a specific storage partition, all of the hosts in that
storage partition are limited to the maximum number of LUNs allowed by the restricted host type.
• You cannot move a host with a restricted host type into a storage partition that already has LUNs mapped that
are greater than what is allowed by the restricted host type. For example, if you have a restricted host type that
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