External storage and data recovery method for external storage as well as program

The data is automatically recovered to a desired arbitrary point in an external storage without imposing a burden on the host computer. An application on a host computer instructs data recovery control processing of a disk control apparatus to set a recovery opportunity. It is possible to register arbitrary plural points as a recoverable point by setting a recovery flag included in journal data. In the case in which data is recovered due to occurrence of a failure or the like, the application requests a list showing recovery opportunities which have already been set. The application designates a point to which data is recovered on the basis of the recovery opportunity list. The disk control apparatus recovers the data to the designated point on the basis of a backup disk and a journal disk.