Extending useful life of a non-volatile memory by health grading

• US 9,558,107 B2
• Filed: 12/24/2013
• Issued: 01/31/2017
• Est. Priority Date: 12/24/2013
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Camp, Charles J., Koltsidas, Ioannis, Papandreou, Nikolaos, Parnell, Thomas, Pletka, Roman A., Pozidis, Charalampos, Tressler, Gary A., Walls, Andrew D.
• Primary Examiner(s): Rojas, Midys
• Application Number:
  US14/139,925
• Publication Number:
  US 20150177995A1
• Time in Patent Office: 1,134 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 11/008 Reliability or availability analysis
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/0766 Error or fault reporting or storing
• CPC Class Codes: G06F 11/0787 Storage of error reports, e.g. persistent data storage, storage using memory protection
• CPC Class Codes: G06F 11/10 Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
• CPC Class Codes: G06F 11/1048 using arrangements adapted for a specific error detection or correction feature
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 12/00 Accessing, addressing or allocating within memory systems or architectures digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0653 Monitoring storage devices or systems

Abstract

In at least one embodiment, a controller of a non-volatile memory array determines, for each of a plurality of regions of physical memory in the memory array, an associated health grade among a plurality of health grades and records the associated health grade. The controller also establishes a mapping between access heat and the plurality of health grades. In response to a write request specifying an address, the controller selects a region of physical memory to service the write request from a pool of available regions of physical memory based on an access heat of the address and the mapping and writes data specified by the write request to the selected region of physical memory.

Claims

1. A method in a data storage system including a non-volatile memory array controlled by a controller, the method comprising:

for each region among a plurality of regions of physical memory in the memory array, the controller;

determining at least one error metric for the region based on read errors generated by host read requests targeting the region that are received by the data storage system from an external host system and recording the at least one error metric for the region;

determining, based on the at least one error metric for the region and based on a number of program/erase cycles for the region, an associated health grade among a plurality of health grades for the region and recording the associated health grade for the region;

the controller establishing a mapping between access heat and the plurality of health grades;

in response to a write request specifying an address, the controller selecting a selected region of physical memory to service the write request from a pool of available regions of physical memory based on an access heat of the address and the mapping; and

the controller writing data specified by the write request to the selected region of physical memory.

2. The method of claim 1, and further comprising changing which health grade is associated with a particular region of physical memory based on a change of the at least one error metric for the particular region of physical memory.

3. The method of claim 1, and further comprising:

the controller determining and recording a heat of each of the plurality of regions of physical memory.

4. The method of claim 1, wherein establishing the mapping includes:

mapping greater access heat to health grades indicating greater health; and

mapping less access heat to health grades indicating less health.

5. A data storage system, comprising:

a controller configured to be coupled to a non-volatile memory array, wherein the controller determines for each region among a plurality of regions of physical memory in the memory array (1) at least one error metric for the region based on read errors generated by host read requests targeting the region that are received by the data storage system from an external host system and (2) an associated health grade among a plurality of health grades based on the at least one error metric for that region of physical memory and based on a number of program/erase cycles for that region, and records the at least one error metric and the associated health grade for each region, and wherein the controller establishes a mapping between access heat and the plurality of health grades and, in response to a write request specifying an address, selects a selected region of physical memory to service the write request from a pool of available regions of physical memory based on an access heat of the address and the mapping, and writes data specified by the write request to the selected region of physical memory.

6. The data storage system of claim 5, wherein the controller changes which health grade is associated with a particular region of physical memory based on a change of the at least one error metric for the particular region of physical memory.

7. The data storage system of claim 5, wherein the controller determines and records a heat of each of the plurality of regions of physical memory.

8. The data storage system of claim 5, wherein the mapping established by the controller maps greater access heat to health grades indicating greater health and maps less access heat to health grades indicating less health.

9. The data storage system of claim 5, and further comprising the non-volatile memory array coupled to the controller.

10. A program product, comprising:

a storage device; and

program code stored in the storage device, wherein the program code, when executed by a controller that controls a non-volatile memory array of a data storage system, causes the controller to perform;

for each region among a plurality of regions of physical memory in the memory array;

determining at least one error metric for the region based on read errors generated by host read requests targeting the region that are received by the data storage system from an external host system and recording the at least one error metric for the region;

determining, based on the at least one error metric for the region and based on a number of program/erase cycles for the region, an associated health grade among a plurality of health and recording the associated health grade for the region;

establishing a mapping between access heat and the plurality of health grades;

in response to a write request specifying an address, selecting a selected region of physical memory to service the write request from a pool of available regions of physical memory based on an access heat of the address and the mapping; and

writing data specified by the write request to the selected region of physical memory.

11. The program product of claim 10, wherein the program code further causes the controller to perform changing which health grade is associated with a particular region of physical memory based on a change of the at least one error metric for the particular region of physical memory.

12. The program product of claim 10, wherein the program code further causes the controller to perform:

determining and recording a heat of each of the plurality of regions of physical memory.

13. The program product of claim 10, wherein establishing the mapping includes:

mapping greater access heat to health grades indicating greater health; and

mapping less access heat to health grades indicating less health.