Abstract: Illustrative embodiments provide a computer implemented method for minimizing loss of access to a storage system during a concurrent controller code load in a redundant dual controller subsystem. The computer implemented method receives a request for a controller code load, verifies all required hosts are connected with the second controller to form a first verification, and responsive to the first verification indicating that all required hosts are connected with the second controller, varies a first controller offline. The controller code load is performed in the first controller, and the first controller is varied back online. The computer implemented method performs a verification that all required hosts are connected with the first controller to form a second verification, and responsive to the second verification indicating that all required hosts are connected with the first controller, varies the second controller offline, and performs the controller code load in the second controller.