Administrator Guide

Working in the Mappings topic
Topics:
• Viewing mappings
• Mapping initiators and volumes
• View map details
Viewing mappings
The Mapping topic shows a tabular view of information about mappings that are defined in the system. By default, the table shows 20
entries at a time and is sorted first by host and second by volume.
The mapping table shows the following information:
• Group.Host.Nickname. Identifies the initiators to which the mapping applies:
○ All Other Initiators. The mapping applies to all initiators that are not explicitly mapped with different settings.
○ initiator-name—The mapping applies to the initiator only.
○ initiator-ID—The mapping applies to the initiator only, and the initiator has no nickname.
○ host-name.*—The mapping applies to all initiators in the host.
○ host-group-name.*.*—The mapping applies to all hosts in this group.
• Volume. Identifies the volumes to which the mapping applies:
○ volume-name—The mapping applies to the volume only.
○ volume-group-name.*—The mapping applies to all volumes in the volume group.
• Access. Shows the type of access assigned to the mapping:
○ read-write—The mapping permits read and write access to volumes.
○ read-only—The mapping permits read access to volumes.
○ no-access—The mapping prevents access to volumes.
• LUN. Shows whether the mapping uses a single LUN or a range of LUNs (indicated by *).
• Ports. Lists the controller host ports to which the mapping applies. Each number represents corresponding ports on both controllers.
To display more information about a mapping, see View map details on page 110.
Mapping initiators and volumes
You can map initiators and volumes to control host access to volumes unless the volume is the secondary volume of a replication set.
Mapping applies to hosts and host groups as well as initiators, and to virtual snapshots and volume groups as well as volumes. For the
purposes of brevity, the terms initiator and volumes will stand in for all possibilities, unless otherwise stated. By default, volumes are not
mapped.
If a volume is mapped to ID All Other Initiators, this is its default mapping. The default mapping enables all connected initiators to see the
volume using the specified access mode, LUN, and port settings. The advantage of a default mapping is that all connected initiators can
discover the volume with no additional work by the administrator. The disadvantage is that all connected initiators can discover the volume
with no restrictions. Therefore, this process is not recommended for specialized volumes that require restricted access. Also, to avoid
multiple hosts mounting the volume and causing corruption, the hosts must be cooperatively managed, such as by using cluster software.
If multiple hosts mount a volume without being cooperatively managed, volume data is at risk for corruption. To control access by specific
hosts, you can create an explicit mapping. An explicit mapping can use different access mode, LUN, and port settings to allow or prevent
access by a host to a volume, overriding the default mapping. When an explicit mapping is deleted, the volume's default mapping takes
effect.
The storage system uses Unified LUN Presentation (ULP), which can expose all LUNs through all host ports on both controllers. The
interconnect information is managed in the controller firmware. ULP appears to the host as an active-active storage system where the
host can choose any available path to access a LUN regardless of disk group ownership. When ULP is in use, the controllers' operating/
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