Controller states

You can place a controller into three different states: online, offline, and service mode.

Online state

The online state is the normal operating state of the controller. It means that the controller is operating normally and is available for I/O operations.

When you place a controller online, its status is set to optimal.

Offline state

The offline state is typically used to prepare a controller for replacement when there are two controllers in the storage array. A controller can enter the offline state in two ways: you can issue an explicit command or the controller can fail. A controller can exit the offline state only by issuing another explicit command or by replacing the failed controller. You can place a controller offline only if there are two controllers in the storage array.

When a controller is in the offline state, the following conditions are true:

Service mode

Service Mode is typically used only by technical support to move all storage array volumes to one controller so that the other controller can be diagnosed. A controller must be manually placed in service mode and must be manually placed back online after the service operation is completed.

When a controller is in service mode, the following conditions are true: