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The following is based on Selective LUN Map. Additional information can be viewed at FAQ: Selective LUN mapping.

Selective LUN Map (SLM) reduces the number of paths from the host to the LUN. With SLM, when a new LUN map is created, the LUN is accessible only through paths on the node owning the LUN and its HA partner.

SLM enables management of a single igroup per host and also supports non-disruptive LUN move operations that do not require portset manipulation or LUN remapping.

Portsets can be used with SLM just as in previous versions of Data ONTAP to further restrict access of certain targets to certain initiators . When using SLM with portsets, LUNs will be accessible on the set of LIFs in the portset on the node that owns the LUN and on that node’s HA partner.

Beginning with Data ONTAP 8.3 SLM is enabled by default on all new LUN maps. For LUNs created prior to Data ONTAP 8.3, you can manually apply SLM by using the lun mapping remove-reporting-nodes command to remove the LUN reporting nodes and restrict LUN access to the LUN owning node and its HA partner.

Example

An SVM has 4 nodes and 16 LIFs per node. The storage administrator creates a portset with 2 LIFs from each node, binds the portset to an igroup, and maps a LUN to the igroup. The LUN is only accessible on the node that owns the LUN and that node’s HA partner through the 4 LIFS specified in the portset.

More information

How to determine whether SLM is enabled on a LUN map
If your environment has a combination of LUNs created in Data ONTAP 8.3 and LUNs transitioned into Data ONTAP 8.3 from previous versions, you might need to determine whether Selective LUN Map (SLM) is enabled on a specific LUN.

cluster::> lun mapping show -vserver <vserver> -fields reporting-nodes

cluster::> lun mapping show -vserver svm01 -fields reporting-nodes

6 entries were displayed.
vserverpathigroupreporting-nodes




svm01/vol/svr01_cv_app/svr01_cv_appsvr01cluster-03,cluster-04
svm01/vol/svr01_cv_index/svr01_cv_indexsvr01cluster-01,cluster-02
svm01/vol/svr02_cv_app/svr02_cv_appsvr02cluster-03,cluster-04
svm01/vol/svr02_cv_index/svr02_cv_indexsvr02cluster-01,cluster-02
svm01/vol/svr_san_boot/svr01svr01
svm01/vol/svr_san_boot/svr02svr02

Decreasing mapped LUN paths with SLM for LUNs created prior to Data ONTAP 8.3 You can reduce the number of paths mapped to your LUNs by using Selective LUN Map (SLM). Reducing the number of LUN paths simplifies host side multipath management and ensures that the number of host paths to the LUN does not exceed the maximum supported by Data ONTAP.

  • If you are modifying reporting nodes you must be in advanced mode

cluster::> set advanced

Warning: These advanced commands are potentially dangerous; use them only when directed to do so by NetApp personnel.
Do you want to continue? {y|n}: y

cluster::*> lun mapping add-reporting-nodes -vserver -path -igroup -local-nodes true

cluster::*> lun mapping show -vserver svm01 -fields reporting-nodes

6 entries were displayed.
vserverpathigroupreporting-nodes




svm01/vol/svr01_cv_app/svr01_cv_appsvr01cluster-03,cluster-04
svm01/vol/svr01_cv_index/svr01_cv_indexsvr01cluster-01,cluster-02
svm01/vol/svr02_cv_app/svr02_cv_appsvr02cluster-03,cluster-04
svm01/vol/svr02_cv_index/svr02_cv_indexsvr02cluster-01,cluster-02
svm01/vol/svr_san_boot/svr01svr01
svm01/vol/svr_san_boot/svr02svr02

cluster::*> lun mapping add -vserver svm01 -path /vol/svr_san_boot/svr01 -igroup svr01 -local-nodes true

cluster::*> lun mapping show -vserver svm01 -fields reporting-nodes

6 entries were displayed.
vserverpathigroupreporting-nodes




svm01/vol/svr01_cv_app/svr01_cv_appsvr01cluster-03,cluster-04
svm01/vol/svr01_cv_index/svr01_cv_indexsvr01cluster-01,cluster-02
svm01/vol/svr02_cv_app/svr02_cv_appsvr02cluster-03,cluster-04
svm01/vol/svr02_cv_index/svr02_cv_indexsvr02cluster-01,cluster-02
svm01/vol/svr_san_boot/svr01svr01cluster-01,cluster-02
svm01/vol/svr_san_boot/svr02svr02

Modifying SLM reporting nodes
If you are moving a LUN or a volume containing LUNs to another HA pair within the same cluster, you should modify the Selective LUN Map (SLM) reporting-nodes list, before initiating the move. This ensures that active/optimized LUN paths are maintained.

FlexPod Boot LUNs

At Red8, it is part of our operational recommendation when configuring FlexPod with 4-Node+ cDOT clusters, and SAN boot, to have boot policies where the primary and secondary paths to the boot LUN are configured to node 1 and node 3 of the cDOT cluster (assumes the boot LUN is configured on node 1). This would allow SAN boot to continue to work over the unoptimized path via the Cluster Interconnect Switch. In a cDOT 8.3 environment, where SLM is enabled by default, this would not be possible. To emulate a pre cDOT 8.3 environment and allow the paths of the boot LUNs to be visible across all nodes you need to modify the reporting nodes.

cluster::*> lun mapping show -fields reporting-nodes,node,lun-id

6 entries were displayed.
vserverpathigrouplun-idnodereporting-nodes






svm01/vol/svr01_cv_app/svr01_cv_appsvr011cluster-03cluster-03,cluster-04
svm01/vol/svr01_cv_index/svr01_cv_indexsvr012cluster-02cluster-01,cluster-02
svm01/vol/svr02_cv_app/svr02_cv_appsvr023cluster-04cluster-03,cluster-04
svm01/vol/svr02_cv_index/svr02_cv_indexsvr024cluster-01cluster-01,cluster-02
svm01/vol/svr_san_boot/svr01svr010cluster-01cluster-01,cluster-02
svm01/vol/svr_san_boot/svr02svr020cluster-02cluster-01,cluster-02

cluster::*> lun mapping add-reporting-nodes -vserver svm01 -path /vol/svr_san_boot/svr* -igroup svr* -all true
2 entries were acted on.

cluster::*> lun mapping show -fields reporting-nodes,node,lun-id

6 entries were displayed.
vserverpathigrouplun-idnodereporting-nodes






svm01/vol/svr01_cv_app/svr01_cv_appsvr011cluster-03cluster-03,cluster-04
svm01/vol/svr01_cv_index/svr01_cv_indexsvr012cluster-02cluster-01,cluster-02
svm01/vol/svr02_cv_app/svr02_cv_appsvr023cluster-04cluster-03,cluster-04
svm01/vol/svr02_cv_index/svr02_cv_indexsvr024cluster-01cluster-01,cluster-02
svm01/vol/svr_san_boot/svr01svr010cluster-01
svm01/vol/svr_san_boot/svr02svr020cluster-02

Disable Selective LUN Map Cluster-wide

Can Selective LUN Map be disabled?

Selective LUN Map (SLM) is enabled by default. Run the following commands to disable LUN Map cluster-wide:

cluster::> set diag

Warning: These diagnostic commands are for use by NetApp personnel only.
Do you want to continue? {y|n}: y

cluster::*> options lun.reporting_nodes.enable off

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