Suspension of an asynchronous remote copy pair system having a primary controller and a remote controller

This invention relates to an asynchronous remote copying (ARC) system adapted to operate as a remote copy pair by communicating between primary storage and remote storage of a remote copy pair. The system comprises a primary controller for receiving a write command and writing data to primary storage; a remote controller for receiving a write command and writing data to remote storage; an ARC controller for suppressing the release of the write command to the remote controller if a delay between receiving the write command and the time when the remote storage may accept the data is more than a threshold delay, and the primary controller suppresses recording the data in primary storage until release of the write command to the remote storage.