Three data center remote copy system with journaling

A remote copy system, comprising:

• a first storage system including a first storage controller and a first data volume, the first storage controller being configured to receive a write request from a first host associated with the first storage system and to store write data associated with the write request to the first data volume;
• a second storage system including a second storage controller and a second data volume, the second storage controller receiving first data containing the write data to mirror the first data volume to the second data volume;
• and
• a third storage system including a third storage controller and a third data volume, the third storage controller receiving second data containing a journal to mirror the first data volume in the third data volume, wherein the journal comprises the write data and a sequence number indicating write ordering to the first data volume;
• wherein the write request from the first host to the first storage system completes after the first data is received by the second storage system;
• wherein the write request from the first host to the first storage system completes independently of the second data being received by the third storage system;
• wherein write data to be stored on the third data volume is generated according to the write order provided by the sequence number of the journal that is contained in the second data.