Memory system managing the number of times of erasing
A memory system according to an embodiment of the present invention comprises: a memory amount required for management table creation is reduced by adopting a nonvolatile semiconductor memory including a plurality of parallel operation elements respectively having a plurality of physical blocks as units of data erasing and a controller that can drive the parallel operation elements in parallel and has a number-of-times-of-erasing managing unit that manages the number of times of erasing in logical block units associated with a plurality of physical blocks driven in parallel.
1. A memory system comprising:
a nonvolatile semiconductor memory area including a plurality of parallel operation elements respectively having a plurality of physical blocks, each of the plurality of physical blocks being a unit of data erasing; and
a controller configured to drive the parallel operation elements in parallel and configured to manage a number of times of erasing in logical block units, each of the logical block units being associated with a plurality of physical blocks driven in parallel; wherein
the controller is configured to perform physical block replacement processing for replacing, when a bad block managed in physical block units occurs in the logical block, the bad block with another physical block in a same parallel operation element, and thereafter acquire a free block as an unallocated logical block and execute replacement of a logical block address of the acquired free block and a logical block address of a logical block subjected to the physical block replacement processing,
the controller includes a free block management table for managing a logical block address of a logical block allocated to the free block and a logical-to-physical translation table for managing, in logical block address units, a correspondence relation between a plurality of physical block addresses corresponding to a plurality of physical blocks and logical block addresses corresponding to logical blocks associated with the physical blocks and the number of times of erasing and an erasing time; and,
the free block management table includes a first list for managing, in erasing time order managed by the logical-to-physical translation table, the logical block address for the logical block allocated to the free block and a second list for managing, in order of a number of times of erasing managed by the logical-to-physical translation table, a logical block address for a logical block overflowing from the first list, and
the controller acquires the free block from the second list.
2. The memory system according to claim 1 , wherein
the controller is configured to acquire, in performing the physical block replacement processing, the other physical block from reserve blocks managed in physical block units.
3. The memory system according to claim 2 , wherein
the controller is configured to register, in performing the physical block replacement processing, one or a plurality of physical blocks excluding the bad block in the logical block as the reserve blocks when another physical block in the same parallel operation element is not present.
4. The memory system according to claim 3 , wherein
the controller is configured to:
acquire a free block after registering one or a plurality of blocks excluding the bad block in the logical block as the reserve blocks;
execute replacement of a logical block address of the acquired free block and a logical block address of the logical block registered as the reserve blocks; and
disable use of the logical block address of the free block.
5. The memory system according to claim 1 , wherein
the controller is configured to maintain, when the physical block replacement processing as replacement of the bad block in physical block units is performed, the number of times of erasing managed in logical block units.
6. The memory system according to claim 1 , wherein
the controller includes a bad block management table for managing, in parallel operation element units, a physical block address of a physical block allocated to the bad block.
7. The memory system according to claim 1 , wherein
the controller includes a reserve block management table for managing, in parallel operation element units, physical block addresses of physical blocks allocated to the reserve blocks.
8. The memory system according to claim 1 , wherein
the nonvolatile semiconductor memory area having a plurality of channel parallel operation elements, each channel parallel operation element includes a plurality of physical blocks, and the controller is configured to select one physical block from each one of the plurality of channel parallel operation elements.
9. The memory system according to claim 1 , wherein
the nonvolatile semiconductor memory area having a plurality of channel parallel operation elements including a plurality of memory chips, each memory chip includes a plurality of planes capable of operating in parallel, each plane includes a plurality of physical blocks, and the controller is configured to select one physical block from each one of the plurality of planes.