1. A method of operating a storage system following a power loss, comprising: preventing receipt of input/output commands; copying content of a cache memory to a local storage device; detecting resumption of an external power supply; charging a local power supply; copying content of the local storage device to a cache memory; processing the content of the cache memory with respect to at least one storage volume to copy the content of the cache memory to the local storage device by a predetermined amount; allowing receipt of the input/output commands using a reduced portion of the cache memory; detecting that a charge stored on the local power supply has reached a predetermined level; and allowing receipt of the input/output commands using all of the cache memory.