Tracking and Utilizing Second Level Map Index for Recycling of Solid State Drive Blocks

• US 20150120989A1
• Filed: 11/27/2013
• Published: 04/30/2015
• Est. Priority Date: 10/31/2013
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Xu, Peng, Tang, Alex Ga Hing, Ma, LiZhao, Shu, Nanshan
• Granted Patent: US 9,606,912 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices

Abstract

A recycling method for a solid state drive is disclosed. The method includes selecting a logical block for recycle wherein the logical block includes a plurality of pages across a plurality of flash dies. The method also includes retrieving an address map index record associated with the logical block selected for recycle. For each particular address map index stored in the address map index record, the recycling method retrieves a set of address map entries referenced by the particular address map index, determines whether any page in the logical block is referenced by the set of address map entries, and if at least one page in the logical block is referenced by the set of address map entries, the method writes the at least one page to a different logical block. The method further includes erasing the plurality of pages in the logical block.

Claims

1. A recycling method for a solid state drive, the method comprising:

selecting a logical block for recycle, the logical block including a plurality of pages across a plurality of flash dies;

retrieving an address map index record associated with the logical block selected for recycle;

for each particular address map index stored in the address map index record, performing the steps of;

retrieving a set of address map entries referenced by the particular address map index;

determining whether any page in the logical block is referenced by the set of address map entries; and

in response to determining that at least one page in the logical block is referenced by the set of address map entries, writing said at least one page to a different logical block; and

erasing the plurality of pages in the logical block.

2. The method of claim 1, wherein the address map is implemented utilizing a two level map and each set of address map entries is organized as a second level mapping page.

3. The method of claim 1, further comprising:

recording at least one address map index in the address map index record associated with the logical block when the logical block is written, said at least one address map index refers to at least one address map entry that refers to a page in the logical block.

4. The method of claim 1, further comprising:

updating the address map index record associated with the logical block.

5. The method of claim 4, wherein updating the address map index record associated with the logical block comprises:

retrieving the address map index record associated with the logical block;

for each particular address map index stored in the address map index record, performing the steps of;

retrieving a set of address map entries referenced by the particular map index;

determining whether any page in the logical block is referenced by the set of address map entries; and

in response to determining that none of the pages in the logical block is referenced by the set of address map entries, removing the particular address map index from the address map index record.

6. The method of claim 1, wherein the solid state drive includes a plurality of logical blocks, each logical block of the plurality of logical blocks being uniquely associated with an address map index record.

7. The method of claim 6, wherein a selection criteria is established for selecting at least one address map index record to update, the selection criteria including at least one of:

a valid page count of the logical block associated with the address map index record, or a difference between an original valid page count and a current valid page count of the logical block associated with the address map index record.

8. A recycling method for a solid state drive, the solid state drive utilizing a two level map for tracking logical address to physical address mapping, the method comprising:

selecting a logical block for recycle, the logical block including a plurality of pages across a plurality of flash dies;

retrieving a second level map (SLM) index record associated with the logical block selected for recycle;

for each particular SLM index stored in the SLM index record, performing the steps of;

retrieving a SLM page referenced by the particular SLM index;

determining whether any page in the logical block is referenced by map entries in the SLM page; and

in response to determining that at least one page in the logical block is referenced by the map entries in the SLM page, writing said at least one page to a different logical block; and

erasing the plurality of pages in the logical block.

9. The method of claim 8, further comprising:

recording at least one SLM index in the SLM index record associated with the logical block when the logical block is written, said at least one SLM index refers to at least one SLM page that refers to a page in the logical block.

10. The method of claim 8, further comprising:

updating the SLM index record associated with the logical block.

11. The method of claim 10, wherein updating the SLM index record associated with the logical block comprises:

retrieving the SLM index record associated with the logical block;

for each particular SLM index stored in the SLM index record, performing the steps of;

retrieving a SLM page referenced by the particular SLM index;

determining whether any page in the logical block is referenced by map entries in the SLM page; and

in response to determining that none of the pages in the logical block is referenced by the map entries in the SLM page, removing the particular SLM index from the SLM index record.

12. The method of claim 8, wherein the solid state drive includes a plurality of logical blocks, each logical block of the plurality of logical blocks being uniquely associated with a SLM index record.

13. The method of claim 12, wherein a selection criteria is established for selecting at least one SLM index record to update, the selection criteria including at least one of:

a valid page count of the logical block associated with the SLM index record, or a difference between an original valid page count and a current valid page count of the logical block associated with the SLM index record.

14. A solid state drive, comprising:

a plurality of flash dies, each of the plurality of flash dies including a plurality of blocks, each of the plurality of blocks further including a plurality of pages for providing data storage; and

a controller for managing a recycle operation for the solid state drive, wherein the recycle operation is performed in units of logical blocks, wherein each logical block includes a plurality of pages across at least a subset of the plurality of flash dies, and wherein upon receiving a recycle request, the controller is configured to;

select a logical block for recycle;

retrieve an address map index record associated with the logical block selected for recycle;

for each particular address map index stored in the address map index record, perform the steps of;

retrieve a set of address map entries referenced by the particular address map index;

determine whether any page in the logical block is referenced by the set of address map entries; and

in response to at least one page in the logical block being referenced by the set of address map entries, write said at least one page to a different logical block; and

erase the plurality of pages in the logical block.

15. The solid state drive of claim 14, wherein the address map is implemented utilizing a two level map and each set of address map entries is organized as a second level mapping page.

16. The solid state drive of claim 14, wherein the controller is further configured to:

record at least one address map index in the address map index record associated with the logical block when the logical block is written, said at least one address map index refers to at least one address map entry that refers to a page in the logical block.

17. The solid state drive of claim 14, wherein the controller is further configured to:

update the address map index record associated with the logical block.

18. The solid state drive of claim 17, wherein the controller updates the address map index record by performing the steps of:

retrieve the address map index record associated with the logical block;

for each particular address map index stored in the address map index record, perform the steps of;

retrieve a set of address map entries referenced by the particular map index;

determine whether any page in the logical block is referenced by the set of address map entries; and

in response to determining that none of the pages in the logical block is referenced by the set of address map entries, remove the particular address map index from the address map index record.

19. The solid state drive of claim 14, wherein the solid state drive includes a plurality of logical blocks, each logical block of the plurality of logical blocks being uniquely associated with an address map index record.

20. The solid state drive of claim 19, wherein a selection criteria is established by the controller to select at least one address map index record to update, the selection criteria including at least one of:

a valid page count of the logical block associated with the address map index record, or a difference between an original valid page count and a current valid page count of the logical block associated with the address map index record.