Method of extending lifetime of solid state disk

• US 10,423,338 B2
• Filed: 12/29/2017
• Issued: 09/24/2019
• Est. Priority Date: 10/24/2017
• Status: Active Grant

• Current Assignee: Apacer Technology Incorporated
• Original Assignee: Apacer Technology Incorporated
• Inventors: Lee, Jiunn-Chang, Liao, Yin-Chuan
• Primary Examiner(s): Tran, Uyen B
• Application Number:
  US15/859,060
• Publication Number:
  US 20190121551A1
• Time in Patent Office: 634 Days
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/14 Circuits for erasing electrically, e.g. erase voltage switching circuits
• CPC Class Codes: G11C 16/16 for erasing blocks, e.g. arrays, words, groups
• CPC Class Codes: G11C 16/3445 Circuits or methods to verify correct erasure of nonvolatile memory cells
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically
• CPC Class Codes: G11C 17/14 in which contents are determined by selectively establishing, breaking or modifying connecting links by permanently altering the state of coupling elements, e.g. PROM
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels
• CPC Class Codes: G11C 2211/5644 Multilevel memory comprising counting devices
• CPC Class Codes: G11C 2216/26 Floating gate memory which is adapted to be one-time programmable [OTP], e.g. containing multiple OTP blocks permitting limited update ability

Abstract

The present disclosure illustrates a method of extending a lifetime of a solid state disk (SSD). The SSD includes a flash memory which is a multi-level cell (MLC) flash memory. The method includes steps of: setting a number of logic blocks of the SSD to be one-half of a number of physical blocks of the flash memory; reading, by a control unit of the SSD, a write/erase times of each of the physical blocks of the flash memory; and converting the physical block, of which a number of the write/erase times exceeds an upper limit of the write/erase times, from a multi-level storage format to a single-level storage format. A number of the logic blocks is a constant value.

Claims

1. A method of extending lifetime of a solid state disk (SSD), and the SSD comprising a flash memory which is a three-level cell (TLC) flash memory, and the method comprising:

setting a number of logic blocks of the SSD to be one-third of a number of physical blocks of the flash memory;

reading, by a control unit of the SSD, a first write/erase times of each of the physical blocks of the flash memory;

converting the physical block, of which a number of the first write/erase times exceeds an upper limit of the first write/erase times, from a three-level storage format to a multi-level storage format;

reading, by the control unit, a second write/erase times of each of the physical blocks converted into the multi-level storage format; and

converting the physical block, which is in the multi-level storage format and a number of the second write/erase times exceeds an upper limit of the second write/erase times, into a single-level storage format;

wherein a number of the logic blocks is a constant value.

2. The method according to claim 1, wherein when all physical blocks are converted into the single-level storage format and a bad block ratio of the physical blocks converted into the single-level storage format is higher than a preset ratio, the SSD enters a read-only state.

3. The method according to claim 1, wherein a capacity of each of the physical blocks in the multi-level storage format is two-thirds of capacity of each of the physical blocks in the three-level storage format, and when all physical blocks are converted into the multi-level storage format, the capacity of the flash memory is reduced to two-thirds.

4. The method according to claim 3, wherein a capacity of each of the physical blocks in the single-level storage format is one-half of capacity of each of the physical blocks in the multi-level storage format, and when all physical blocks are converted into the single-level storage format, the capacity of the flash memory is equal to a logic access capacity of the SSD.