Server User Manual

132 Configuration: Disk Groups and Virtual Disks
# 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 MDSM, or delete the LUN if necessary.
6 If you want to map another LUN or increase volume capacity, perform this
action from MDSM.
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
8
Use the multipath -ll command to verify that:
• If a new LUN is mapped, the new LUN is detected and given a multi-
pathing device node
• If you increased volume capacity, the new capacity is displayed.
Restricted Mappings
Many hosts are able to map up to 256 logical unit numbers (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 9-3 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 9-3. Mapping Restrictions
Guidelines when you work with host types with LUN mapping restrictions:
Operating System Highest LUN
Windows Server 2003 and Windows server 2008 255
Linux 255
book.book Page 132 Tuesday, June 18, 2013 3:03 PM