Memory system and method for controlling a nonvolatile semiconductor memory

A memory system comprising:

• a nonvolatile semiconductor memory including a plurality of storage units;
• a volatile semiconductor memory including a storage area;
• a controller configured to:
• select valid data stored in first storage units;
• store write data in the storage area, the write data being sent from a host apparatus;
• write the selected valid data, as first valid data, in a second storage unit, when a sum of the valid data stored in the first storage units does not reach a size of a unit of storage;
• copy, as second valid data, the write data stored in the storage area, to the second storage unit, when the write data stored in the storage area reaches a size of a unit of management of the valid data;
• and
• write the first valid data and the second valid data stored in the second storage unit, in a third storage unit, when a total size of the first valid data and the second valid data stored in the second storage unit reaches the size of the unit of storage.

A compaction method comprising:

• storing data in a nonvolatile semiconductor memory, the nonvolatile semiconductor memory including a plurality of storage units;
• selecting valid data stored in first storage units;
• storing write data in a storage area included in a volatile semiconductor memory, the write data being sent from a host apparatus;
• writing the selected valid data, as first valid data, in a second storage unit, when a sum of the valid data stored in the first storage units does not reach a size of a unit of storage;
• copying, as second valid data, the write data stored in the storage area, to the second storage unit, when the write data stored in the storage area reaches a size of a unit of management of the valid data;
• and
• writing the first valid data and the second valid data stored in the second storage unit, in a third storage unit, when a total size of the first valid data and the second valid data stored in the second storage unit reaches the size of the unit of storage.

A memory system comprising:

• a controller;
• a first nonvolatile storage unit;
• a second nonvolatile storage unit;
• and
• a third nonvolatile storage unit;
• wherein
• the controller is configured to:
• write first data, as first valid data, from the first nonvolatile storage unit, in the second nonvolatile storage unit, when a sum of the first data does not reach a first size;
• write second data, as second valid data, from an external device, in the third nonvolatile storage unit, when the second data reaches a second size;
• and
• write the first valid data and the second valid data, in the third nonvolatile storage unit, when a total size of the first valid data and the second valid data reaches the first size.