Patent ID: 8028139

Claim:
A remote copy system comprising: a first storage system being adapted to be coupled to a first host computer and having a first logical volume accompanied with a first plurality of disk drives in the first storage system; a second storage system having a second logical volume accompanied with a second plurality of disk drives in the second storage system and a virtual volume not accompanied with the second plurality of disk drives, the virtual volume configuring a first remote copy pair with the first logical volume; and a third storage system being adapted to be coupled to a second host computer and having a third logical volume accompanied with a third plurality of disk drives in the third storage system and a fourth logical volume accompanied with the third plurality of disk drives, the fourth logical volume configuring a second remote copy pair with the virtual volume, wherein, if the first storage system receives a write data sent from the first host computer to the first logical volume, the first storage system stores the write data in the first plurality of disk drives and sends the write data to the second storage system according to a synchronous remote copy procedure, wherein, if the second storage system receives the write data sent from the first storage system, the second storage system does not store the write data in the virtual volume, stores the write data in the second logical volume, which maintains the write data temporarily, and sends the write data of the second logical volume to the third storage system according to an asynchronous remote copy procedure, wherein, if the third storage system receives the write data sent from the second storage system, the third storage system stores the write data in the third logical volume, which maintains the write data temporarily, and stores the write data of the fourth logical volume so that the fourth logical volume stores a duplicated data of data stored in the first logical volume, and wherein, when a failure occurs in the first storage system, the second storage system sends the write data stored in the second logical volume to the third storage system before the second host computer takes over for the first host computer by using the fourth logical volume.