Why are there I/O reads from passive paths when using device-mapper-multipath on Red Hat Enterprise Linux?

Solution Unverified - Updated -

Issue

  • Need guidance on how to manage path groups with priority for certain prio numbers.
  • lower priority, passive paths have data being written to them.
  • noticing I/O on both active and passive paths

Environment

  • Red Hat Enterprise Linux 5 (RHEL5)
  • SAN providing multiple paths to a storage device.

  • device-mapper-multipath managing paths.

    • Either default or specifically configured to use directio or readsector0 path checkers.
    • Does not apply to multipath devices using TUR path checker.
    devices {
        # NetApp
        device {
                vendor                  "NETAPP"
                product                 "LUN"
                path_grouping_policy    group_by_prio
                features                "1 queue_if_no_path"
                prio_callout            "/sbin/mpath_prio_alua /dev/%n"
                path_checker            directio
                path_selector           "round-robin 0"
                failback                immediate
                hardware_handler        "1 alua"
                rr_weight               uniform
                rr_min_io              128
                getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"
        }
}

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