Patent ID: 7213110

Claim:
A destaging method for destaging a storage apparatus system including a plurality of disk storage devices for storing data, coupled to a disk control apparatus which controls said disk storage devices, a first cache memory, included in said disk control apparatus, that temporarily stores input/output data to and from the disk storage devices and a network attached storage (NAS) server which is connected to the disk control apparatus and has a second cache memory that temporarily stores data read from the disk control apparatus and is coupled to a client computer having a third cache memory that temporarily stores data read from the NAS server, the destaging method comprising: a first step of, when an interruption of a data storage function of the disk control apparatus for the NAS server occurs, receiving from the client computer data that is scheduled to be written onto the disk apparatus and currently stored in the third cache memory and storing the data in the second cache memory; a second step of transferring to the first cache memory data that is currently stored in the second cache memory and that is scheduled to be written onto the disk storage devices; a third step of managing data to be stored in the disk storage devices by dividing the data into a plurality of management groups; and a fourth step of, when all data that belongs to one of the management groups remaining in the second cache memory and scheduled to be written onto the disk storage devices are ready in the first cache memory, starting to write onto the disk storage devices the data that belongs to the one of the management groups, remaining in the first cache memory and scheduled to be written.