HP StorageWorks 12000 Gateway Virtual Library System User Guide (AH814-96018, December 2012)

LUN Path Failover
LUN path failover allows the VLS to automatically reroute data traffic usually assigned to one
(preferred) path to another (secondary) path when the preferred path fails. Path status is shown in
Command View VLS under Storage LUN Details.
A failover is indicated in the Storage LUN Details screen by the yellow warning icon and the
notification message: Fibre Channel Path Failed Over to {#:#:#:#}. The #s stand for the node port;
bus number (always 0); the target id (an array port); and the LUN number on the array.
When one path fails, automatic failover reroutes data traffic to the secondary path so the data
transfer still happens, but potentially at a slower rate. It is advised that you restore the path as soon
as possible to avoid a double path failure.
To restore the failed path:
1. Determine the cause of the failure and repair it if needed.
2. In Command View VLS, access the System tab.
3. Select Storage LUNs from the navigation tree.
4. Select View to display the storage LUN details.
5. Select Fix Primary Paths from the task bar to display the Fix Primary Paths Wizard.
6. Select Apply to set all paths back to their primary paths.
Failure of both paths (double path failure) is indicated by the red critical icon and a specific
notification message. The notification message differs based on whether the failure occurs while
running or upon booting the system.
• A double path failure that occurs while running results in the critical alert Fibre Channel Paths
Failed for Lun, ulid <numerical LUN id number> wwnn <numerical wwnn>.
• A double path failure that occurs upon booting the system results in the critical alert Missing
Storage LUN paths on node #.
This means the node can not communicate with the LUN at all. If the failed paths are on the primary
node, the whole storage pool containing that LUN is off-line; if the failed paths are on a secondary
node, the storage pool is on-line until reboot, but the storage pool is inaccessible from that node.
In this case, you can still get to the LUNs, but only from a different node.
To repair double path failure (assuming there has been no reboot during the failure):
1. Determine the cause of the failures and repair them if needed.
2. In Command View VLS, access the System tab.
3. Select Storage LUNs from the navigation tree.
4. Select Fix Primary Paths from the task bar to display the Fix Primary Paths Wizard.
5. Select Apply to set all paths back to their original settings.
CAUTION: If you attempt to reboot during a path failure without first repairing the failure, the
array might reassign paths or fail-over preferences. This will limit device performance because all
data traffic will be routed through a single controller. To restore performance, from Command
View EVA:
1. Reset path fail-over preferences for each LUN to no preference.
2. Save the presentation.
3. Reset the path fail-over preferences back to their original values.
4. Save the presentation.
5. Reboot the VLS system.
Managing High Availability 101