Administrator Guide

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

Restricted mappings

Many hosts are able to map up to 256 LUNs (0–255) per storage partition. However, the maximum number of mappings differs because

of operating system variables, multipath 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.

Table 13. Highest lun of operating systems

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 (0–255) 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 more 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 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 allows only LUNs up to 31, you cannot move

that restricted host type into a storage partition that has LUNs greater than 31 already mapped.

Disk groups, standard virtual disks, and thin virtual disks