Memory defect management using signature identification
View Patent ↗A non-volatile storage subsystem is disclosed that implements a process for reliably managing memory defect information. In one embodiment, a list indicating the locations of defective memory locations is stored in a non-volatile storage device along with a signature that can be used to identify the location of the stored defect list. The stored list may relate to memory defects that are associated with, or developed in connection with, a manufacturing process of the storage device. The signature may be stored in a metadata portion of one or more pages in which the list is stored.
1. In a solid-state drive system comprising a non-volatile storage medium comprising a plurality of blocks, each block comprising a plurality of pages having a metadata portion and a data portion, a method of maintaining memory defect information on a non-volatile storage medium, the method comprising:
locating defective blocks on the non-volatile storage medium;
storing at least a first portion of a list of the defective blocks in the data portion of a first page, the list of defective blocks comprising at least some of located defective blocks; and
storing a signature comprising an identifier in the metadata portion of the first page, wherein the signature identifies the first page as a page that contains the first portion of the list of defective blocks.
2. The method of claim 1 , further comprising searching the non-volatile storage medium for the signature and generating a replacement list of defective blocks when the signature is not found.
3. The method of claim 1 , further comprising storing a value that corresponds to the size of the list of defective blocks in the metadata portion of the first page.
4. The method of claim 1 , further comprising storing a second portion of the list of defective blocks in the data portion of a second page.
5. The method of claim 4 , further comprising storing the signature in the metadata portion of the second page.
6. The method of claim 1 , wherein the signature comprises a predetermined value associated with the list of defective blocks.
7. The method of claim 1 , wherein locating defective blocks comprises identifying a value in one or more of the plurality of pages that indicates that a block in which the one or more of the plurality of pages is located is defective.
8. The method of claim 7 , wherein the value was initially stored by a manufacturer of the non-volatile storage medium.
9. The method of claim 1 , wherein the list of defective blocks comprises a list of addresses corresponding to physical locations of the defective blocks.
10. The method of claim 1 , further comprising erasing a set of blocks of the non-volatile storage medium that are not identified as defective.
11. The method of claim 1 , further comprising updating the list of defective blocks in response to detection of a defective block of memory to reflect the defective block of memory, wherein the defective block of memory became defective after the list of defective blocks has been stored.
12. A solid-state drive comprising:
a non-volatile storage medium comprising a plurality of pages having a metadata portion and a data portion; and
a controller configured to:
scan the non-volatile storage medium for a page that comprises a signature that indicates that the page includes at least a portion of a memory defects list;
access the memory defects list when the signature is identified; and
when the signature is not identified:
locate defective blocks on the non-volatile storage medium;
store a list of the defective blocks in the data portion of at least one page; and
store a signature comprising an identifier that identifies the list of defective blocks in the metadata portion of at least one page.
13. The solid-state drive of claim 12 , wherein the controller is configured to scan the non-volatile storage medium in response to receiving a request from a host system.
14. The solid-state drive of claim 13 , wherein the request comprises a vendor specific command not included in a command set of a storage interface between the host system and the non-volatile storage medium.
15. In a solid-state drive system comprising a non-volatile storage medium comprising a plurality of blocks, each block comprising a plurality of pages having a metadata portion and a data portion, a method of maintaining memory defect information on a non-volatile storage medium, the method comprising:
locating defective blocks on the non-volatile storage medium;
storing at least a first portion of a list of the defective blocks in the data portion of a first page, the list of defective blocks comprising at least some of located defective blocks; and
storing a signature in the metadata portion of the first page, wherein the signature identifies the first page as a page that contains the first portion of the list of defective blocks; and
updating the list of defective blocks in response to detection of a defective block of memory to reflect the defective block of memory, wherein the defective block of memory became defective after the list of defective blocks has been stored, and wherein a copy of the list of defective blocks is not updated thereby maintaining an initial list of defective blocks.
16. The method of claim 15 , wherein the signature comprises an identifier.
17. The method of claim 15 , wherein the initial list of defective blocks comprises a manufacturer list of bad blocks identified during manufacture of the solid-state drive system.