Symmetrical devices can provide automatic failback to a possible optimal path. If a failover occurs on the initial path, the standby path becomes the new online path. Usually the standby path is a suboptimal path. When automatic failback is enabled, the initial path comes back online and failover to the initial path automatically occurs.
# mpathadm list mpath-support mpath-support: libmpscsi_vhci.so
# mpathadm modify mpath-support -a on libmpscsi_vhci.so
# mpathadm show mpath-support libmpscsi_vhci.so mpath-support: libmpscsi_vhci.so Vendor: Sun Microsystems Driver Name: scsi_vhci Default Load Balance: round-robin Supported Load Balance Types: round-robin logical-block Allows To Activate Target Port Group Access: yes Allows Path Override: no Supported Auto Failback Config: 1 Auto Failback: on Failback Polling Rate (current/max): 0/0 Supported Auto Probing Config: 0 Auto Probing: NA Probing Polling Rate (current/max): NA/NA Supported Devices: Vendor: SUN Product: T300 Revision: Supported Load Balance Types: round-robin Vendor: SUN Product: T4 Revision: Supported Load Balance Types: round-robin . . .
This operation is applicable only to devices in the following two categories:
Asymmetric devices with a proprietary failover mechanism recognized and supported by multipathing support
Devices conforming to the T10 Standard Target Port Group Support libmpscsi_vhci.so and providing explicit mode asymmetric LU access
# mpathadm list lu /dev/rdsk/c0t600144F08069703400004E828EE10004d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600144F08069703400004E8183DF0002d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600A0B800026D63A0000A4994E2342D4d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800029065C00007CF54E234013d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 Total Path Count: 4 Operational Path Count: 4 . . .
# mpathadm show lu /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 Logical Unit: /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 mpath-support: libmpscsi_vhci.so Vendor: SUN Product: CSM200_R Revision: 0660 Name Type: unknown type Name: 600a0b800026d63a0000a4984e234298 Asymmetric: yes Current Load Balance: round-robin Logical Unit Group ID: NA Auto Failback: on Auto Probing: NA Paths: Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63c Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63c Override Path: NA Path State: OK Disabled: no Target Port Groups: ID: 5 Explicit Failover: yes Access State: active Target Ports: Name: 200800a0b826d63b Relative ID: 0 Name: 200800a0b826d63c Relative ID: 0 ID: 15 Explicit Failover: yes Access State: standby Target Ports: Name: 200900a0b826d63b Relative ID: 0 Name: 200900a0b826d63c Relative ID: 0
# mpathadm failover lu /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2
If this operation is successful, the access state of the device's target port groups changes as a result of the logical unit failover.
# mpathadm show lu /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 Logical Unit: /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 mpath-support: libmpscsi_vhci.so Vendor: SUN Product: CSM200_R Revision: 0660 Name Type: unknown type Name: 600a0b800026d63a0000a4984e234298 Asymmetric: yes Current Load Balance: round-robin Logical Unit Group ID: NA Auto Failback: on Auto Probing: NA Paths: Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63c Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63c Override Path: NA Path State: OK Disabled: no Target Port Groups: ID: 5 Explicit Failover: yes Access State: standby Target Ports: Name: 200800a0b826d63b Relative ID: 0 Name: 200800a0b826d63c Relative ID: 0 ID: 15 Explicit Failover: yes Access State: active Target Ports: Name: 200900a0b826d63b Relative ID: 0 Name: 200900a0b826d63c Relative ID: 0
If the path to a LU is disabled, the enable command changes the path back to enabled. The full path must be specified using the initiator port name, target port name, and the LU. To verify the change, run the show command for the logical unit.
# mpathadm list lu /dev/rdsk/c0t600144F08069703400004E828EE10004d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600144F08069703400004E8183DF0002d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600A0B800026D63A0000A4994E2342D4d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800029065C00007CF54E234013d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800029065C00007CF44E233FCFd0s2 Total Path Count: 4 Operational Path Count: 4 . . .
# mpathadm show lu Logical Unit: /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 mpath-support: libmpscsi_vhci.so Vendor: SUN Product: CSM200_R Revision: 0660 Name Type: unknown type Name: 600a0b800026d63a0000a4984e234298 Asymmetric: yes Current Load Balance: round-robin Logical Unit Group ID: NA Auto Failback: on Auto Probing: NA Paths: Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63c Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63c Override Path: NA Path State: OK Disabled: no Target Port Groups: ID: 5 Explicit Failover: yes Access State: standby Target Ports: Name: 200800a0b826d63b Relative ID: 0 Name: 200800a0b826d63c Relative ID: 0 ID: 15 Explicit Failover: yes Access State: active Target Ports: Name: 200900a0b826d63b Relative ID: 0 Name: 200900a0b826d63c Relative ID: 0
# mpathadm enable path -i 210000e08b841feb -t 200900a0b826d63b \ -l /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2
This operation disables the LU path, regardless of its operational state.
# mpathadm list lu /dev/rdsk/c0t600144F08069703400004E828EE10004d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600144F08069703400004E8183DF0002d0s2 Total Path Count: 8 Operational Path Count: 8 /dev/rdsk/c0t600A0B800026D63A0000A4994E2342D4d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800029065C00007CF54E234013d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800026D63A0000A4984E234298d0s2 Total Path Count: 4 Operational Path Count: 4 /dev/rdsk/c0t600A0B800029065C00007CF44E233FCFd0s2 Total Path Count: 4 Operational Path Count: 4 . . .
# mpathadm show lu /dev/rdsk/c0t600A0B800029065C00007CF34E233F89d0s2 Logical Unit: /dev/rdsk/c0t600A0B800029065C00007CF34E233F89d0s2 mpath-support: libmpscsi_vhci.so Vendor: SUN Product: CSM200_R Revision: 0660 Name Type: unknown type Name: 600a0b800029065c00007cf34e233f89 Asymmetric: yes Current Load Balance: round-robin Logical Unit Group ID: NA Auto Failback: on Auto Probing: NA Paths: Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63b Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200800a0b826d63c Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b841feb Target Port Name: 200900a0b826d63c Override Path: NA Path State: OK Disabled: no Target Port Groups: ID: 8 Explicit Failover: yes Access State: standby Target Ports: Name: 200800a0b826d63b Relative ID: 0 Name: 200800a0b826d63c Relative ID: 0 ID: 18 Explicit Failover: yes Access State: active Target Ports: Name: 200900a0b826d63b Relative ID: 0 Name: 200900a0b826d63c Relative ID: 0
# mpathadm disable path -i 210000e08b841feb -t 200900a0b826d63b \ -l /dev/rdsk/c0t600A0B800029065C00007CF34E233F89d0s2