Triangular asynchronous replication

摘要

Disclosed is a method of recovering data backed up to a local data store and a remote data store. The method first determines which of the local and the remote stores has the most up-to-date data. The data is then copied from the up-to-date store to the other. Determining which of the stores has the most up to date data may involve examining a token from the remote store that indicates the amount of data stored on remote store that is not stored locally. The data copied may be indicated by a plurality of maps indicating the data written to the remote store that is not acknowledged as being written to the local store and/or written to the local store and not acknowledged by the remote store. The data to be stored may in the form of chunks covering preset time periods.