132 Configuration: Disk Groups and Virtual Disks
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
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.
Operating System Highest LUN
Windows Server 2003 and Windows server 2008 255
Linux 255
book.book Page 132 Wednesday, May 26, 2010 2:14 PM