Systems and methods for identifying storage resources that are not in use
An apparatus, system, and method are disclosed for managing a non-volatile storage medium. A storage controller receives a message that identifies data that no longer needs to be retained on the non-volatile storage medium. The data may be identified using a logical identifier. The message may comprise a hint, directive, or other indication that the data has been erased and/or deleted. In response to the message, the storage controller records an indication that the contents of a physical storage location and/or physical address associated with the logical identifier do not need to be preserved on the non-volatile storage medium.
1. A method for managing data in a block-based NAND flash storage system, the method comprising:
identifying, at a host processor, a file to be deleted, and
issuing, by the host processor, an empty-block directive to a solid-state storage controller in response to identifying the file to be deleted, the empty-block directive including a logical block identifier for a logical block corresponding to the file to be deleted; and
storing, by a solid-state storage controller, data pertaining to a logical address space at respective physical addresses of a NAND flash storage medium in response to requests from the host processor;
receiving the empty-block directive at the solid-state storage controller; and
updating, by the solid-state storage controller, a table mapping logical identifiers to physical NAND flash storage locations, wherein the table is updated to assign logical addresses of the logical address space to physical addresses in use to store data on the NAND flash storage medium and, in response to receiving the empty-block directive, to indicate that data stored in one or more of the physical NAND flash storage locations associated with the block identifier do not need to be preserved.
2. The method of claim 1 , wherein responsive to receiving a read command including the block identifier from the host processor after updating the table mapping logical identifiers, the solid-state storage controller returns a data string comprising data bits with a predetermined logic level.
3. The method of claim 2 , wherein the predetermined logic level is zero.
4. The method of claim 1 , wherein at least a part of the table is maintained in volatile memory.
5. The method of claim 1 , wherein the empty-block directive issued by the host processor further comprises an indication that data stored in the one or more physical NAND flash storage locations associated with the block identifier should be overwritten.
6. The method of claim 1 , wherein the empty-block directive is part of a block storage protocol.
7. The method of claim 1 , wherein the empty-block directive is issued at an application programming interface of the host processor.
8. The method of claim 1 , wherein the empty-block directive is issued by a file system of the host processor.
9. The method of claim 1 , wherein the empty-block directive is issued by a storage client of the host processor.
10. The method of claim 1 , further comprising the solid-state storage controller performing garbage collection in the NAND flash storage system.
11. The method of claim 10 , wherein performing garbage collection comprises the solid-state storage controller:
copying a block containing data that should be preserved from an erase block comprising blocks containing data that does not need to be preserved; and
erasing the erase block.
12. The method of claim 11 , further comprising the solid-state storage controller writing data to the erased erase block.
13. The method of claim 1 , wherein the NAND flash storage system is an append-only storage system.
14. The method of claim 1 , wherein each of the one or more physical NAND flash storage locations are smaller than a NAND flash erase block.
15. A system comprising:
a host processor;
a NAND flash storage device; and
a solid-state storage controller;
wherein the host processor is configured to:
identify a file to be deleted, and
issue an empty-block directive to the solid-state storage controller in response to identifying the file to be deleted, the empty-block directive including a logical block identifier for a logical block corresponding to the file to be deleted; and
the solid-state storage controller is configured to:
store data pertaining to a logical address space at respective physical addresses of a NAND flash storage medium in response to requests from the host processor;
update a table mapping logical identifiers to physical NAND flash storage locations, wherein the table is updated to assign logical addresses of the logical address space to physical addresses in use to store data on the NAND flash storage device and, in response to receiving the empty-block directive, to indicate that data stored in one or more of the physical NAND flash storage locations associated with the block identifier do not need to be preserved;
receive the empty-block directive, and
update a table mapping logical identifiers to physical storage locations of the NAND flash storage device, wherein the table is updated to assign logical addresses of the logical address space to physical addresses in use to store data on the NAND flash storage device and, in response to receiving the empty-block directive, to indicate that data stored in one or more physical NAND flash storage locations associated with the block identifier do not need to be preserved.
16. The system of claim 15 , wherein the solid-state storage controller is configured such that, responsive to receiving a read command including the block identifier from the host processor, the solid-state storage controller returns a data string comprising data bits with a predetermined logic level after updating the table.
17. The system of claim 16 , wherein the predetermined logic level is zero.
18. The system of claim 15 , wherein at least a part of the predetermined the table is maintained in volatile memory.
19. The system of claim 15 , wherein the empty-block directive issued by the host processor further comprises an indication that data stored in the one or more physical NAND flash storage locations associated with the block identifier should be overwritten.
20. The system of claim 15 , wherein the empty-block directive is part of a block storage protocol.
21. The system of claim 15 , wherein the host is configured to issue the empty-block directive at an application programming interface of the host processor.
22. The system of claim 15 , wherein a file system of the host processor is configured to issue the empty-block directive.
23. The system of claim 15 , wherein a storage client of the host processor is configured to issue the empty-block directive.
24. The system of claim 15 , wherein the solid-state storage controller is configured to perform garbage collection in the NAND flash storage system.
25. The system of claim 24 , wherein the solid-state storage controller is configured to perform the garbage collection by performing steps comprising:
copying a block containing data that should be preserved from an erase block comprising blocks containing data that does not need to be preserved; and
erasing the erase block.
26. The system of claim 25 , wherein the solid-state storage controller is further configured to write data to the erased erase block.
27. The system of claim 15 , wherein the NAND flash storage system is an append-only storage system.
28. The system of claim 15 , wherein each of the one or more physical NAND flash storage locations are smaller than a NAND flash erase block.