Data synchronization of multiple remote storage

A processing system, comprising:

• a local site having a local host and a local storage system, the local storage system having a primary volume and receiving write data from the local host to the primary volume;
• and
• at least two remote sites, each having a remote host computer and a remote storage system, each remote storage system including a mirrored volume of the primary volume for storing a copy of the write data,
• the local site operable to send one or more commands to each of the remote sites to cause a copy of the write data to be stored on their respective mirrored volumes,
• each of the remote storage systems having one or more queues for queuing information used to produce the copy of write data,
• one of the remote storage systems communicating to another of the remote storage systems information relating to the queued information in order to identify differences between data images maintained by each of the mirrored volumes.

A data storage method, comprising:

• receiving a write request at a local site comprising a local host and a local storage system, the write request having associated write data, the local storage system having a primary volume to which the write data is written;
• communicating first information from the local site to two or more remote sites, each remote site comprising a remote host computer and a remote storage system, each remote storage system including a mirrored volume of the primary volume;
• and
• in response to the first information, creating a copy of the write data to be stored in the mirrored volume of each remote site, including, at each remote site, queuing information that is used to create the copy of the write data to be stored on its mirrored volume.