The present invention provides a method and apparatus for setting up a Peer-to-Peer Remote Copy (PPRC) session and snapshot copying a remote secondary volume to another volume on the remote subsystem. The apparatus includes a primary storage subsystem having a primary data-storage device with at least...http://www.google.de/patents/US6131148?utm_source=gb-gplus-sharePatent US6131148 - Snapshot copy of a secondary volume of a PPRC pair
