Patent ID: 8386815

Claim:
A method of operating a storage system by a processor device, comprising: detecting a cut in an external power supply; switching to a local power supply in a first instance; preventing receipt of input/output commands in a first instance; copying content of a cache memory to a local storage device; marking the content of the cache memory with one of a first state flag indicating cached data that is hardened and designated to be written to the local storage device and a second state flag indicating cached data that is hardened and already in a file in the local storage device; detecting resumption of the external power supply; charging the local power supply; copying content of the local storage device to the cache memory; processing the content of the cache memory with respect to at least one storage volume; receiving input/output commands; detecting a second cut in the external power supply; switching to the local power supply in a second instance; preventing receipt of input/output commands in a second instance; and copying to the local storage device only the content of the cache memory that has the first state flag.