A host and a storage system each keep a shared identifier indicating a state of a system. The storage system acquires, at update of data, a data pair including data for a change through processing of the host and data before the update. The storage system relates the data pair to a shared identifier....http://www.google.de/patents/US7185227?utm_source=gb-gplus-sharePatent US7185227 - Data restoring method and an apparatus using journal data and an identification information
