Memory system and control method thereof

• US 9,280,292 B2
• Filed: 04/10/2015
• Issued: 03/08/2016
• Est. Priority Date: 12/28/2007
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kitsunai, Kazuya, Kanno, Shinichi, Yano, Hirokuni, Hida, Toshikatsu, Yano, Junji
• Primary Examiner(s): CHOE, YONG J
• Application Number:
  US14/683,286
• Publication Number:
  US 20150212746A1
• Time in Patent Office: 333 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A memory system includes a nonvolatile memory including a plurality of blocks as data erase units, a measuring unit which measures an erase time at which data of each block is erased, and a block controller which writes data supplied from at least an exterior into a first block which is set in a free state and whose erase time is oldest.

Claims

1. A memory system comprising:

an interface unit which receives data from outside of the memory system;

a nonvolatile memory including a plurality of blocks as data erase units;

a measuring unit which measures an erase time for at least part of the blocks, the erase time being measured when the block is erased; and

a controller which selects a first block from a plurality of blocks based on the erase time for the blocks, erases data stored in the selected first block, and then writes data which the interface unit received in the first block wherein the controller selects the first block having the oldest erase time.

2. The memory system according to claim 1, wherein the erase time corresponds to an order of the erase operation executed on the blocks, and the controller selects the first block which has the oldest order.

3. The memory system according to claim 1, wherein the controller further selects a second block based on the erase time from a predetermined number of in-use state blocks, selects a third block based on the erase time for the blocks from a predetermined number of free state blocks, and then moves data stored in the second block to the third block.

4. The memory system according to claim 3, wherein the controller selects the second block having the oldest erase time from a predetermined number of in-use state blocks and selects the third block having the oldest erase time from predetermined number of free state blocks.

5. The memory system according to claim 3, wherein the erase time corresponds to order of the erase operation executed on the blocks, and the controller selects the second block having the oldest order from the predetermined number of in-use state blocks and selects the third block having the oldest order from the predetermined number of free state blocks.

6. A method for controlling a nonvolatile memory which includes a plurality of blocks as data erase units, comprising:

measuring an erase time for at least part of the blocks of the nonvolatile memory when the block is erased;

selecting a first block from a plurality of blocks based on the erase time for the blocks;

erasing data stored in the selected first block; and

writing data in the first block wherein the first block has been the oldest erase time.

7. The method according to claim 6, wherein the erase time corresponds to an order of the erase operation executed on the block, and the first block has the oldest order.

8. The method according to claim 6, further comprising selecting a second block based on the erase time from a predetermined number of in-use state blocks, and selecting a third block based on the erase time for the blocks from a predetermined number of free state blocks, and then moving data stored in the second block to the third block.