1. A storage apparatus for storing data transmitted from one or more host computers, comprising: one or more flash memory packages having a plurality of flash memory chips, a storage area provided by the one or more flash memory packages including a first area that is an area for storing actual data formed by one or more logical devices and a second area that is an area for storing a write log data based on a write instruction, the first and second areas being provided in each of the one or more flash memory packages; a reclamation process section executing a reclamation process for overwriting a predetermined memory area with data stored in the second area, to make portions of the second area available for storing subsequent data; a monitoring section monitoring a frequency at which the reclamation process occurs; and a changing section for changing a size of the second area dynamically according to the frequency at which the reclamation process occurs.