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How to verify Linux fibre channel configurations with multipathing I/O (MPIO)

  1. Last updated
    Jun 22, 2021
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Category:
data-ontap-8
Specialty:
san
Last Updated:
6/22/2021, 3:52:50 PM

Applies to

  • SAN
  • Data ONTAP 8 7-Mode
  • FlexPod
  • Data ONTAP 7 and Earlier

Description

Syslog and EMS messages

[hostname: scsitarget.partnerPath.misconfigured:error]: FCP Partner Path Misconfigured.
[hostname: scsitarget.partnerPath.misconfigured:error]: FCP Partner Path Misconfigured - Host I/O access through a non-primary and non-optimal path was detected.

Please see the article, What do FCP Partner Path Misconfigured messages mean?

Terminology 

  • Partner Path:  Any path to LUNs that utilizes the partner node to access a LUN hosted by the local node.  The LUNs are in an active-active cluster.
  • Non-primary path:  Synonymous with partner path, proxy path and secondary path.  All are examples of a non-primary path.
  • FCP target port:  The fibre channel interface that provides FCP service to hosts.
  • Virtual Target Interconnect (VTIC) - The virtual FCP target interface seen in the initiator group list.  VTIC is used to indicate that the initiator has access to a secondary path.

Problem Description

SANs often provide multiple paths to allow hosts to access LUNs. To maximize the redundancy of the SAN, the host operating system must use multipathing I/O (MPIO) software. MPIO software monitors all available paths and will decide which path should be used for the operating system.  Linux distributions based on the 2.6 series kernel make use of the device mapper plug-in known as dm-multipath. Dm-multipath groups paths of equal priority to allow load balancing of I/O, in addition to path failover. Dm-multipath uses a callout program such as mpath_prio_netapp or mpath_prio_ontap to differentiate primary and secondary paths. The system must perform all I/O to this LUN using device mapper devices (e.g. /dev/mapper/mpath0) in order for dm-multipath to route to the SCSI devices belonging to the primary paths.  The following process outlines how to observe the MPIO configuration. Steps to setup the MPIO configuration are documented in the FCP Linux Host Utilities.

 

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