Does Data ONTAP use multipathing software to control the different paths? How can multiple paths to the array disks be confirmed?
NetApp V-Series systems are designed to have more than one path to the array disks. Data ONTAP does not use a separately installed multipath software for VSeries disk path management. It uses built-in path management functionality.
Two paths to the array are a requirement for V-Series installations. This provides redundancy and allows for array and fabric upgrades to be accomplished without disruption. There cannot be more than two paths visible from the V-Series to the array.
Each V-Series has a primary and secondary path to the disks. If the primary path fails, then the secondary path is used. The LUNs are accessed through one port at a time. The paths can be viewed on the V-Series system by using the storage show disk -p all command.
filer> storage show disk -p
------------------------- ---- ------------------------- ----- ---------
switch1-rtp:51.127L0 - switch2-rtp:115.127L0 - - -
switch1-rtp:51.127L1 - switch2-rtp:115.127L1 - - -
switch1-rtp:51.127L2 - switch2-rtp:115.127L2 - - -
switch1-rtp:51.127L3 - switch2-rtp:115.127L3 - - -
switch1-rtp:51.127L4 - switch2-rtp:115.127L4 - - -
switch1-rtp:51.127L5 - switch2-rtp:115.127L5 - - -
switch1-rtp:51.127L6 - switch2-rtp:115.127L6 - - -
switch1-rtp:51.127L7 - switch2-rtp:115.127L7 - - -
switch1-rtp:51.127L8 - switch2-rtp:115.127L8 - - -
This output can be used to verify both primary and secondary paths to the array. The current data path to L0 is through the switch1-rtp switch (fabric). The secondary failover path is through the switch2-rtp switch (fabric).
The path selection is controlled by Data ONTAP. Therefore, the administrator does not need to control the paths to the LUNs manually. Both paths can be fully utilized by Data ONTAP according to the load-balancing algorithms within Data ONTAP.
Comprehensive details on V-Series paths are available in the V-Series Systems Planning Guide for each Data ONTAP version.