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126 Configuration: Disk Groups and Virtual Disks
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If a new LUN is mapped or volume capacity is changed, run the following
command:
# rescan_dm_devs
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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 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.
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
Operating System Highest LUN
Windows Server 2003 and Windows server 2008 255
Linux 255
book.book Page 126 Tuesday, September 27, 2011 3:25 PM