Patent ID: 8407402

Claim:
A memory system comprising: a nonvolatile semiconductor memory configured to store a management table in which management information including storage positions of data stored in the nonvolatile semiconductor memory is recorded; and a controller configured to perform data transfer between a host apparatus and the nonvolatile semiconductor memory and to perform management of data stored in the nonvolatile semiconductor memory based on the management table, wherein the nonvolatile semiconductor memory is configured to store data associated with a first logical address accessible from the host apparatus by a normal command and to store data associated with a second logical address inaccessible from the host apparatus by the normal command, and when receiving an erasing command from the host, the controller compacts data associated with the second logical address by rewriting the data associated with the second logical address within a predetermined area of the nonvolatile semiconductor memory to fit in a predetermined number of logical blocks and thereafter initializes the management table except for a section in the management table information corresponding to the second logical address.