Patent ID: 7143254
Filing Date: 2006-11-28
Classification: G06F,Y10S

Abstract:
1. A data processing system comprising: a first storage system that is connected to a first host device and sends and receives data to and from the first host device; a second storage system that is connected to a second host device and the first storage system and receives data from the first storage system; and a third storage system that is connected to the first storage system and receives data from the first storage system, wherein the first storage system includes a first storage area that stores data sent from the first host device, and a second storage area that stores the data written in the first storage area and update information relating to the data written in the first storage area, the second storage system includes a third storage area that stores data sent from the first storage system, and a fourth storage area that stores the data written in the third storage area and update information relating to the data written in the third storage area, and the third storage system includes a fifth storage area that stores data read from the second storage area and update information relating to the data read from the second storage area, and a sixth storage area that stores data that is generated based on the data written in the fifth storage area and the update information relating to the data written in the fifth storage area, wherein the update information written in the second storage area in the first storage system includes an update number that is generated by the first storage system to be used for identifying a data update order, the data update information written in the fourth storage area in the second storage system includes the update number included in the data update information written in the second storage area, and the data update information written in the fifth storage area in the third storage system includes the update number included in the data update information written in the second storage area, wherein, when the first storage system fails, the third storage system sends to the second storage system latest update information relating to the update information written in the fifth storage area, and the second storage system judges, based on the latest update information sent from the third storage system and by using data written in the fourth storage area, as to whether data update for the fifth storage area in the third storage system is possible, wherein, when the second storage system judges by using the data written in the fourth storage area that data update for the fifth storage area in the third storage system is possible, the third storage system controls to read from the second storage system data that is not written in the fifth storage area and update information relating thereto among the data and the update information relating thereto written in the fourth storage area in the second storage system, wherein the second storage system writes in the third storage area data sent from the second host device, and writes in the fourth storage area the data written in the third storage area and update information relating to the data written in the third storage area, wherein data writing in the third storage area in the second storage system is performed asynchronously with data writing in the sixth storage area in the third storage system, and wherein the second storage system sends to the third storage system the data written in the fourth storage area and the update information relating to the data written in the fourth storage area, and wherein the third storage system writes in the fifth storage area the data and the update information relating thereto sent from the second storage system, and writes in the sixth storage area data generated based on the data and the update information relating thereto written in the fifth storage area.