Patent ID: 8397012

Claim:
A method of operating a data storage subsystem, said method comprising: allocating less than all of a volatile memory for storing hardened data to be preserved in the event of power interruption to said data storage subsystem; in response to a power loss to said data storage subsystem, transferring said hardened data from said volatile memory to a non-volatile memory, wherein said volatile memory and said non-volatile memory are powered by a battery during said data transfer; and in response to a power restore to said data storage subsystem after said power loss, permitting said hardened data within said volatile memory only to be read when not all of said hardened data in said volatile memory are guaranteed to be backup to said non-volatile memory in case of another power loss while said battery is being recharged; and permitting said hardened data within said volatile memory to be read or written when all of said hardened data in said volatile memory are guaranteed to be backup to said non-volatile memory in case of another power loss while said battery is being recharged.