Patent ID: 7467168

Claim:
A method for mirroring data, comprising: processing a mirror policy indicating volumes in a first storage system to mirror to volumes in a second storage system and volumes in the second storage system to mirror to volumes in a third storage system, wherein the third storage system is at a first geographical location remote with respect to a second geographical location including the first and second storage systems, and wherein the mirror policy indicates volumes in the third storage system to mirror to volumes in a fourth storage system at the second geographical location; performing an initial copy operation to copy volumes in the mirror policy from the first storage system to the second storage system and to copy the volumes in the mirror policy to a third storage system; transmitting a command to cause the copying of updates to the volumes in the first storage system to corresponding volumes in the second storage system indicated in the mirror policy in response to completing the copying of the volumes in the mirror policy to the second storage system; upon an occurrence of an event, causing the suspension of the copying of updates to the volumes in the first storage system indicated in the mirroring policy to the volumes in the second storage system to form a consistency group of updates between volumes in the second and third storage systems that is consistent as of a point in time with the volumes in the first storage subsystem; and during the suspension of the copying of volumes between the first and second storage systems, causing the copying of updates to the volumes in the second storage system indicated in the mirroring policy, which comprise the updates to the volumes in the first storage system, from the second storage system to the volumes in the third storage system indicated in the mirroring policy to form the consistency group of updates among volumes in the first, second and third storage systems as of the point-in-time; determining whether the copying of the updates to the volumes in the first storage system from the second storage system to volumes in the third storage system has completed; causing the end of the suspension to cause the continuation of the copying of updates to the volumes in the first storage system to the volumes in the second storage system in response to completing the copying of the updates to the volumes in the first storage system from the second storage system to the third storage system; determining whether the copying of the updates to the volumes in the second storage system to volumes in the third storage system has complete; and making a copy of the volumes in the third storage system indicated in the mirroring policy to the volumes in the fourth storage system indicated in the mirroring policy to harden the consistency group in the fourth storage system, where a consistency group of data as of a point-in-time is maintained in the volumes in the first, second, third, and fourth storage subsystems.