SYSTEM AND METHOD FOR USING OVER-PROVISIONED DATA CAPACITY TO MAINTAIN A DATA REDUNDANCY SCHEME IN A SOLID STATE MEMORY

• US 20120151254A1
• Filed: 12/14/2010
• Published: 06/14/2012
• Est. Priority Date: 12/14/2010
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: HORN, ROBERT L.
• Granted Patent: US 8,601,311 B2
• Time in Patent Office: Days
• US Class Current: 714/6.22
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence

Abstract

Redundant “parity” RAID (5, 6, 50, 60) is a well-known technique for increasing data reliability beyond the failure rate of an individual storage device. In many implementations of redundant RAID, when a storage element is lost, a replacement or spare element is required to restore redundancy. A typical solid state storage device is over-provisioned with more storage media than is required to satisfy the specified user capacity. Embodiments of the present invention utilize the additional over-provisioned capacity and potentially modify the stripe size to restore RAID redundancy when a storage element or path (i.e., page, block, plane, die, channel, etc.) has failed. In some cases, this may also involve reducing the RAID stripe size.

Claims

1. A solid-state storage subsystem comprising:

a non-volatile memory array comprising a user data quota portion and an over-provisioning quota portion, each quota portion comprising a plurality of solid-state storage elements; and

a controller configured to;

implement a data redundancy configuration with a plurality of data stripes, each data stripe comprising a respective subset of the plurality of storage elements of the user data quota portion; and

be responsive to a failure of a storage element of the user data quota portion by at least;

replacing the failed storage element of the user data quota portion with one of the storage elements of the over-provisioning quota portion; and

rebuilding one or more of the data stripes that include the failed storage element using the storage element from the over-provisioning quota portion.

2. The solid-state storage subsystem of claim 1, wherein the controller is further configured to perform the replacement of storage elements and rebuilding of data stripes only when a capacity of the over-provisioning quota portion is above a pre-defined minimum size, the pre-defined minimum being a value that exceeds an amount needed to replace a storage element.

3. The solid-state storage subsystem of claim 1, wherein the storage elements comprise a plurality of pages, blocks, dies, devices or channels.

4. The solid-state storage subsystem of claim 1, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.

5. A method of maintaining data redundancy in a solid-state storage subsystem in the event of a storage element failure, the method comprising:

dividing a non-volatile memory array of the solid-state storage subsystem into a user data quota portion and an over-provisioning quota portion, each quota portion comprising a plurality of storage elements, the user data quota portion storing a plurality of stripes that are arranged in accordance with a data redundancy configuration, each data stripe comprising a respective subset of the plurality of storage elements in the user data quota portion; and

in response to detecting a failure in a storage element in the user data quota portion,

removing the failed storage element from one or more of the data stripes that include the failed storage element; and

rebuilding the one or more data stripes.

6. The method of claim 5, further comprising:

prior to rebuilding the one or more data stripes, determining if a capacity of the over-provisioning quota portion is above a pre-defined minimum size, the pre-defined minimum being a value that exceeds an amount needed to replace a storage element.

7. The method of claim 5, wherein the storage elements comprise a plurality of pages, blocks, dies, devices or channels.

8. The method of claim 7, further comprising:

prior to rebuilding the one or more data stripes, replacing the failed storage element with a storage element from the over-provisioning quota portion when the failed storage element is a die, a device, or a channel.

9. The method of claim 5, wherein the data redundancy configuration is a redundant array of independent disks (RAID) configuration.