1. A method of a controller coupled between a host server and a data store comprising: solely packing blocks of a cache memory of the controller corresponding to a dirty data in an order of a volume number and a logical block address within a volume, the dirty data being data from the host server prior to being written to the data store; backing up the packed blocks of the cache memory corresponding to the dirty data in a intermediary backup non-volatile storage device distinct from both the cache memory and the data store and storing packing information in the intermediary backup non-volatile storage device, with storing of the packing information at the cache memory being avoided; maintaining, in the packing information, a state of the packed blocks of the cache memory corresponding to the dirty data immediately prior to a power outage during the power outage; and sequentially accessing the packed blocks of the cache memory corresponding to the dirty data in the intermediary backup non-volatile storage device based on the packing information to transfer the dirty data to the data store following restoration of power.