DYNAMIC HIGHER-LEVEL REDUNDANCY MODE MANAGEMENT WITH INDEPENDENT SILICON ELEMENTS

• US 20130246839A1
• Filed: 11/30/2011
• Published: 09/19/2013
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Werner, Jeremy Isaac Nathaniel, Baryudin, Leonid, Canepa, Timothy Lawrence, Cohen, Earl T.
• Granted Patent: US 9,105,305 B2
• Time in Patent Office: Days
• US Class Current: 714/6.13
• CPC Class Codes: G06F 11/1044 with specific ECC/EDC distribution
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G11B 20/1883 Methods for assignment of alternate areas for defective areas
• CPC Class Codes: H03M 13/353 Adaptation to the channel

Abstract

A Solid-State Disk (SSD) controller enables dynamic higher-level redundancy mode management with independent silicon elements to provide graceful degradation as non-volatile (e.g. flash) memory elements fail during operation of an SSD implemented by the controller. Higher-level error correction provides correction of lower-level uncorrectable errors. If a failure of one of the non-volatile memory elements is detected, then the higher-level error correction is dynamically transitioned from operating in a current mode to operating in a new mode. The transition includes one or more of reducing free space available on the SSD, rearranging data storage of the SSD, recovering/storing failed user data (if possible), and determining/storing revised higher-level error correction information. Operation then continues in the new mode. If another failure of the non-volatile memory elements is detected, then another transition is made to another new mode.

Claims

1. A system comprising:

means for computing k redundant data portions to protect n-k useful data portions;

means for storing each of the k redundant data portions and each of the n-k useful data portions in separate corresponding areas, each of the corresponding areas in a respective one of n physical devices;

means for, subsequent to a failure such that one of the corresponding areas is no longer usable, computing j redundant data portions to protect n-1-j useful data portions; and

wherein j<

=k.

2. The system of claim 1, wherein the means for computing k redundant data portions to protect n-k useful data portions is operable in a first data protection mode, the means for computing j redundant data portions to protect n-1-j useful data portions is operable in a second data protection mode, and further comprising means for, in response to the failure, switching from operating in the first data protection mode to operating in the second data protection mode.

3. The system of claim 1, wherein when j==k, a total amount of the useful data portions is decreased and a degree of protection is at least preserved.

4. The system of claim 3, wherein the degree of protection is protection against failures of up to j of the corresponding areas.

5. The system of claim 1, wherein when j==k-1 and j>

=1, a total amount of the useful data portions is preserved, a degree of protection is decreased, and the useful data portions are protected.

6. The system of claim 5, wherein the decreased degree of protection is protection against failures of up to j-1 of the corresponding areas.

7. The system of claim 1,

wherein each of the n physical devices comprises a plurality of the corresponding areas;

further comprising means for storing, in each of a plurality of sets of the corresponding areas, a respective set of data comprising a useful data subset and a redundant data subset protecting the useful data subset, the redundant data subset stored in distinct ones of the n physical devices from the useful data subset; and

wherein each of the sets of the corresponding areas comprises no more than one corresponding area of each one of the n physical devices, and the means for storing is in accordance with each of the respective sets of data optionally being stored in a different set of n or less of the n physical devices.

8. The system of claim 7, wherein prior to the failure, the useful data subset of a particular one of the sets of data comprises the n-k useful data portions, and the redundant data subset of the particular set of data comprises the k redundant data portions.

9. The system of claim 7, wherein the means for storing is in accordance with a first one of the corresponding areas in a particular one of the n physical devices being used to store a portion of the useful data subset of a first one of the sets of data, and is further in accordance with a second one of the corresponding areas in the particular physical device being used to store a portion or all of the redundant data subset of a second one of the sets of data.

10. The system of claim 7, wherein an amount of storage in a first one of the corresponding areas differs from an amount of storage in a second one of the corresponding areas.

11. The system of claim 10, wherein the first corresponding area and the second corresponding area are in a same one of the n physical devices.

12. A system comprising:

means for operating in a first higher-level redundancy mode comprising means for storing n information portions in n respective non-overlapping areas of memory;

means for operating in a second higher-level redundancy mode comprising means for storing n-1 information portions in n-1 respective non-overlapping areas of the memory;

means for detecting a failure of a failing one of the n respective non-overlapping areas;

means for, in response to the failure, dynamically transitioning from operating via the means for operating in the first higher-level redundancy mode to operating via the means for operating in the second higher-level redundancy mode, the n-1 of the n respective non-overlapping areas being the n respective non-overlapping areas excluding the failing one of the n respective non-overlapping areas;

wherein each of the n information portions comprises respective n-k data information portions and respective k redundant information portions computed to protect the respective n-k data information portions;

wherein each of the n-1 information portions comprises respective n-1-j data information portions and respective j redundant information portions computed to protect the respective n-1-j data information portions;

wherein j<

=k; and

wherein each of the n respective non-overlapping areas is in a respective one of n physical devices of the memory.

13. The system of claim 12, wherein when j==k, a total amount of the data information portions is decreased and a degree of protection is at least preserved.

14. The system of claim 13, wherein the degree of protection is protection against failures of up to j of the n respective non-overlapping areas.

15. The system of claim 12, wherein when j==k-1 and j>

=1, a total amount of the data information portions is preserved, a degree of protection is decreased, and the data information portions are protected.

16. The system of claim 15, wherein the decreased degree of protection is protection against failures of up to j-1 of the n respective non-overlapping areas.

17. A system comprising:

means for managing one or more flash memories in accordance with a current higher-level redundancy mode in response to read and/or write requests from a computing host; and

means for dynamically transitioning the current higher-level redundancy mode in response to detecting a failure of one or more portions of one or more of the flash memories.

18. The system of claim 17, wherein the means for dynamically transitioning comprises means for reducing free space.

19. The system of claim 17, wherein the means for dynamically transitioning comprises means for rearranging data storage in accordance with a target higher-level redundancy mode.

20. The system of claim 17, wherein the means for dynamically transitioning comprises means for determining and storing revised higher-level redundancy information in accordance with a target higher-level redundancy mode.