I/O data path protection to redundant controllers in a storage subsystem is accomplished with the Auto-Logical Drive Transfer (ADT) feature and a host multi-path driver.
ADT is a built-in feature of the controller firmware that manages individual logical drives on a storage subsystem. When it is enabled and used in conjunction with a host multi-path driver, it helps ensure that an I/O data path is available for the logical drives on the storage subsystem. When you create a logical drive, you assign a controller to own the logical drive (called the preferred controller or preferred owner
Note: Ensure that there is a multi-path driver installed on each host connected to the storage subsystem. If ADT is not enabled, the I/O data path will still be protected as long as you use the multi-path RDAC driver supplied with the storage management software. However, when an I/O request is sent to an individual logical drive and there is a problem along the data path to its preferred controller, all of the logical drives on that controller will be transferred to the other controller instead of just that particular logical drive.