A method for resynchronizing a first copy of data on a first storage system from a second copy of the data on a second storage system includes, at a regular checkpoint interval, the first storage system pushing data in its cache that were modified prior to a checkpoint time to its nonvolatile storage and saving the checkpoint time to its nonvolatile storage. The method further includes, at a regular snapshot interval greater than the checkpoint interval, the second storage system taking snapshots of the second copy of the data. When the first storage system has an uncontrolled shutdown, the second storage system determines the snapshot closest in time to the last checkpoint time and sends the difference between the last snapshot and the second copy of the data to the first storage system to recover data lost during the uncontrolled shutdown.