Log structured reserved zone for a data storage device

• US 9,880,926 B1
• Filed: 08/20/2013
• Issued: 01/30/2018
• Est. Priority Date: 08/20/2013
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Venkata, Sumanth Jannyavula
• Primary Examiner(s): Tsai, Sheng-Jen
• Application Number:
  US13/971,601
• Time in Patent Office: 1,624 Days
• Field of Search: 711103
• 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 2212/7211 Wear leveling

Abstract

A circuit may be configured to store data to a reserved zone of a non-volatile solid state memory (NVSSM) in a log structured manner and to use information stored in the reserved zone to restore data as needed. In some embodiments, a reserved area of a NVSSM may include die from one or more non-volatile memory modules, which can be divided into blocks and the blocks can be combined to form frames. In some examples, the frames may contain frame headers that can contain a unique identifier which can indicate which frame is to be used to restore data structures, such as during power up or for other restore events.

Claims

1. An apparatus comprising:

a data storage device (DSD) including;

nonvolatile solid state memory (NVSSM) having a selected portion of storage capacity designated as a reserved zone of physical memory blocks reserved for system data and distributed across multiple die, the reserved zone divided into multiple frames, each frame having a unique identifier (UID) and including one or more of the physical memory blocks;

a controller configured to;

maintain the reserved zone as a log structured reserve zone distinct from a remaining portion of the storage capacity, such that once a last frame of the reserved zone is programmed, the system data is then stored to a first frame of the reserved zone; and

set a value of the UID for a current frame to be larger than the values of the UIDs of the other frames of the reserved zone each time system data is stored, such that a frame with the largest UID is a most recently programmed frame.

2. The apparatus of claim 1 further comprising the controller configured to:

store the system data to a selected frame in the log structure when a threshold number of write commands are received.

3. The apparatus of claim 2 further comprising the controller configured to:

determine if the system data is successfully stored to the selected frame;

when the system data is successfully stored, select a next frame in the log structure for storing next system data; and

when the system data is not successfully stored, perform an error check for the selected frame.

4. The apparatus of claim 3 further comprising the controller configured to:

count a number of write commands received from a host;

when the threshold number of write commands have been received from the host, the controller is configured to perform a store operation including;

erase the selected frame;

store the system data to the selected frame; and

determine if the system data is successfully stored at the selected frame.

5. The apparatus of claim 4 further comprising the controller configured to:

when the store operation is not successful;

determine when a threshold number of successive unsuccessful store operations has been exceeded;

when the threshold number of successive unsuccessful store operations has been exceeded;

disable the reserved zone such that the DSD can no longer store system data therein;

when there have been less than the threshold number of successive unsuccessful store operations;

disable the selected frame such that the selected frame will not be used for future store operations;

select a next frame in the log structure; and

perform the store operation at the next frame.

6. The apparatus of claim 5 further comprising the controller configured to:

program the selected frame to a selected location;

increment a location of the selected frame by one to a next frame;

program the next frame to another location; and

when the last frame is programmed to a location, select the first frame to store the next system data.

7. The apparatus of claim 6 further comprising the controller configured to:

scan locations in the reserved zone to determine a first frame with a largest UID of the frames;

determine if the first frame is valid;

when the first frame is valid, restore data structures from system data stored within the first frame; and

when the first frame is not valid, determine a second frame having a next largest UID, and when the second frame is valid, restore data structures from system data stored within the second frame.

8. The apparatus of claim 7 further comprising:

the system data in each frame includes;

a defect map;

a program-erase (PE) cycle counter;

one or more counters;

one or more event logs; and

a frame header.

9. The apparatus of claim 8 further comprising the controller configured to:

store a UID in each frame header.

10. The apparatus of claim 9 further comprising the controller configured to:

when a recovery process is triggered, scan only storage locations containing frame headers to determine a frame with the largest UID.

11. An apparatus comprising:

nonvolatile solid state memory (NVSSM) having a reserved zone including multiple memory blocks reserved for system data and distributed across multiple die, the reserved zone divided into multiple frames, each including one or more memory blocks;

a controller configured to;

maintain the reserved zone as a log structured reserve zone, such that once a last frame of the reserved zone is programmed, system data is then stored to a first frame of the reserved zone;

store a unique identifier (UID) in a frame header of each written frame;

set a value of the UID of a current frame to be larger than the values of the UIDs of the other frames of the reserved zone each time system data is stored, such that a frame with a largest UID is a most recently programmed frame;

when a recovery process is triggered, scan storage locations containing frame headers to determine the frame with the largest UID; and

restore data structures from system data stored within the frame with the largest UID.

12. The apparatus of claim 11 further comprising:

the memory blocks in a frame are wholly stored in a die that does not contain blocks from other frames.

13. The apparatus of claim 11 further comprising:

the blocks in a frame are wholly stored in a die that contains blocks from other frames.

14. The apparatus of claim 11 further comprising:

the blocks in a frame are stored in multiple die such that some blocks in the frame are stored in one die and other blocks are stored in another die; and

a portion of the frame is stored on a die that contains portions of another frame.

18. The Apparatus of claim 11 comprising the controller further configured to:

when a trigger to perform a store operation occurs;

store system data to a selected frame of the reserved zone;

determine if the system data is successfully stored at the selected frame; and

when the store operation is not successful;

disable the reserved zone when a threshold number of successive unsuccessful operations has been exceeded.

19. The apparatus of claim 18 further comprising:

when the store operation is not successful, the controller further configured to;

disable the selected frame when there have been less than the threshold number of successive unsuccessful operations;

select a next frame in the log structure; and

perform the store operation at the next frame.

15. A method comprising:

storing system data to a reserved zone of a nonvolatile solid state memory (NVSSM), the reserved zone having multiple physical blocks distributed across multiple die and reserved for system data, the multiple physical blocks divided among multiple frames;

storing the system data to the multiple frames in a log structure such that once a last frame in the log structure is programmed, the system data is then stored to a first frame in the log structure;

when a store operation is not successful;

determining a number of successive unsuccessful operations;

when a threshold number of successive unsuccessful store operations has been exceeded;

disabling the reserved zone such that the reserved zone can no longer store system data;

when the threshold number of successive unsuccessful operations has not been exceeded;

disabling a selected frame such that the selected frame will not be used to store system data; and

selecting a next frame in the log structure to store the system data.

16. The method of claim 15 further comprising:

implementing the reserved zone across the multiple physical blocks as part of a wear leveling process;

storing the system data to a selected frame in the log structure when a threshold number of write commands are received, the threshold number based on a capacity of the NVSSM;

when the system data is successfully stored to the NVSSM, selecting a next location in the log structure for storing next system data; and

when the system data is not successfully stored in the NVSSM, performing an error check for the selected frame.

17. The method of claim 15 further comprising:

storing a unique identifier (UID) in a frame header of each written frame;

setting a value of the UID for a current frame to be larger than the values of the UIDs of the other frames of the reserved zone each time system data is stored, such that a frame with a largest UID is a most recently programmed frame;

when a recovery process is triggered, determining a valid frame with the largest UID, including;

scanning locations in the reserved zone to determine a first frame with a largest UID of the frames;

determining if the first frame is valid based on detected read errors;

when the first frame is not valid, determining validity of a next frame having a next largest UID until a valid frame is located; and

restore data structures based on system data stored within the valid frame with the largest UID.