A storage device and method for ensuring the provision of data as complete files in a storage device capable of processing both block input/output I/O and file I/O. For each logical volume, an attempt is made to unmount logical units (LUs) storing files triggered by a session start request for block I/O (login request) such as iSCSI, and to recognize (mount) files of logical units triggered by a session completion request for block I/O (Logout request). Block access processing units may also create a replication of a specified logical unit and set a relevant replicated logical unit as a logical unit for access.