Patent ID: 7278049

Claim:
A method of recovery from a data storage system failure in a data storage system having a host computer writing updates to a local storage controller associated with a local storage device at a local site, the local storage controller a synchronously copying the updates to a remote storage controller at a remote site, the remote storage controller storing the updates on a remote storage device and periodically storing a consistent point in time copy of the updates on a backup storage device, the method comprising: detecting a failure associated with the local site; terminating copying the updates from the local storage controller to the remote storage controller; establishing a reverse asynchronous copy relationship from the remote storage controller to the local storage controller; determining whether an intact consistency group exists on the backup storage device at the time the failure is detected; forming a new intact consistency group if an intact consistency group does not exist on the backup storage device at the time the failure is detected; removing inconsistent data from the remote storage device by performing a reverse point in time copy operation from the backup storage device to the remote storage device; recording post-failure updates processed by the remote storage controller; correcting the failure associated with the local site; and copying changed data from the remote storage device to the local storage device to resynchronize the local storage device with the remote storage device.