Selective LUN Mapping (SLM) is a NetApp ONTAP feature that controls which nodes in a cluster report paths to a specific LUN. By default, a LUN is accessible through all nodes in the cluster that host a SAN LIF. When SLM is configured for a LUN, it restricts path reporting to only the node that owns the LUN and its high-availability (HA) partner. This ensures that the host only sees paths through the local HA pair, which is the most optimal configuration for performance and path management, preventing unnecessary traffic across the cluster interconnect.

B. Subsystem: An NVMe subsystem is a collection of controllers and namespaces. While it defines what an initiator can access, it does not inherently restrict presentation to an HA pair.

C. Consistency group: A consistency group is used to manage a set of LUNs together for data protection purposes, such as creating simultaneous, write-order-consistent snapshots. It does not control LUN access paths.

D. igroup: An initiator group (igroup) controls which hosts (initiators) are permitted to access a LUN. It does not control which ONTAP nodes present the paths to that LUN.

1. NetApp ONTAP 9 Documentation

SAN administration

"How Selective LUN Map works": "By default

when you map a LUN to an initiator group (igroup)

the LUN is accessible through network paths to the node that owns the LUN and to all other nodes in the cluster... You can use Selective LUN Map (SLM) to reduce the number of paths from the host to the LUN. SLM makes the LUN accessible only through paths on the node that owns the LUN and the node’s HA partner."

2. NetApp Technical Report TR-4333

"NetApp SAN Best Practices

" Page 11

Section 2.4.1 Selective LUN Mapping: "Selective LUN Mapping (SLM) limits the number of paths to a LUN to only the nodes in the HA pair that own the LUN. By default

ONTAP advertises paths to all nodes in the cluster. SLM is recommended for all configurations."

3. NetApp ONTAP 9 Documentation

SAN administration

"What initiator groups are": "An initiator group (igroup) is a collection of worldwide port names (WWPNs) for Fibre Channel (FC) initiators or iSCSI qualified names (IQNs) for iSCSI initiators. You use igroups to control which hosts have access to a LUN." This reference clarifies the function of an igroup

distinguishing it from SLM.