A storage system maintains a journal of journal entries and at least one snapshot of one or more data volumes. By assigning a unique sequence number to journal and snapshot, it is easy to find a journal which can be applied to the snapshot. A technique is described for detecting an overflow condition...http://www.google.com.au/patents/US7111136?utm_source=gb-gplus-sharePatent US7111136 - Method and apparatus for backup and recovery system using storage based journaling
