Patent ID: 7958306
Filing Date: 2011-06-07
Classification: G06F

Abstract:
1. A storage system comprising: a first storage apparatus, coupled to a host computer, including first volumes; a second storage, coupled to the first storage apparatus, including second volumes and managing asynchronous pairs between the first volumes and the second volumes for storing replication data of the first volumes to the second volumes by an asynchronous remote copy; and a third storage apparatus, coupled to the first storage apparatus, including third volumes and managing synchronous pairs between the first volumes and the third volumes for storing replication data of the first volumes to the third volumes by a synchronous remote copy, wherein the third storage apparatus stores difference data between the third volumes and the second volumes, which is used to start an asynchronous remote copy of differential pairs between the third volumes to the second volumes, wherein the third storage apparatus stores differential pair statuses of the differential pairs, wherein normal statuses of the differential pair statuses indicate that the third storage apparatus and the second storage apparatus are replicating data between the second volumes and the third volumes by the asynchronous remote copy of the differential pairs, wherein ready statuses of the differential pair statuses indicate that the third storage apparatus and the second storage apparatus are ready for starting the asynchronous remote copy of the differential pairs, wherein abnormal statuses of the differential pair statuses indicate that the third storage apparatus and the second storage apparatus are not ready for starting the asynchronous remote copy of the differential pair, and wherein according to changing the differential pair statuses from the abnormal statuses to the ready statuses, the first storage apparatus and the second storage apparatus and the third storage apparatus count a number of the first volumes, a number of the second volumes and a number of the third volumes, for checking the numbers are equal.