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Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

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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 1. Highest lun of operating systemsThe highest LUN of Windows Server 2003, Windows Server 2008, and Linux is 255.
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.

The Default Group on the Host Mappings tab has a default host type. To change the host type, right-click on the host and select Change Default Host Operating System from the pop-up menu. If you set the default host type to a host type that is restricted, the maximum number of LUNs allowed in the Default Group for any host is restricted to the limit imposed by the restricted host type. If a particular host with a nonrestricted host type becomes part of a specific storage partition, you are able to change the mapping to a higher LUN.

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