If a controller is in the offline state or in service mode, you can place it back online.
If the graphic shows the drives, click Show back of shelf.
The graphic changes to show the controllers instead of the drives.
Click a controller that is in either the offline state or service mode.
The controller’s context menu appears.
Select Place online, and confirm that you want to perform the operation.
Detection of a restored preferred path by the multipath driver can take up to 10 minutes.
Any volumes originally owned by this controller are automatically moved back to the controller as I/O requests are received for each volume. In some cases, you might need to manually redistribute the volumes with the Redistribute volumes command.