LOGICAL SECTOR MAPPING IN A FLASH STORAGE ARRAY

• US 20130042052A1
• Filed: 08/11/2011
• Published: 02/14/2013
• Est. Priority Date: 08/11/2011
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Ethan Miller
• Inventors: Colgrove, John, Hayes, John, Miller, Ethan, Wang, Feng
• Granted Patent: US 8,788,788 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 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 2212/50 Control mechanisms for virtual memory, cache or TLB
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0638 Organizing or formatting or addressing of data
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A system and method for efficiently performing user storage virtualization for data stored in a storage system including a plurality of solid-state storage devices. A data storage subsystem supports multiple mapping tables. Records within a mapping table are arranged in multiple levels. Each level stores pairs of a key value and a pointer value. The levels are sorted by time. New records are inserted in a created newest (youngest) level. No edits are performed in-place. All levels other than the youngest may be read only. The system may further include an overlay table which identifies those keys within the mapping table that are invalid.

Claims

1. A computer system comprising:

a data storage medium;

a data storage controller coupled to the data storage medium; and

a mapping table that includes a plurality of entries, each of the mapping table entries comprising a tuple including a key;

wherein the mapping table is organized as a plurality of time ordered levels, each level comprising one or more mapping table entries.

2. The computer system as recited in claim 1, further comprising a cache configured to store a cached copy of at least a portion of the mapping table.

3. The computer system as recited in claim 1, wherein in response to receiving a request, the data storage controller is further configured to:

access the mapping table with at least a given key corresponding to the request;

identify one or more entries that correspond to the given key;

determine which of the one or more entries corresponds to a youngest level of the time ordered levels; and

return an entry that corresponds to the youngest level of the time ordered levels to satisfy the request.

4. The computer system as recited in claim 3, wherein the controller is configured to sort each level by tuple key value.

5. The computer system as recited in claim 4, wherein entries of the mapping table stored in a storage medium are grouped into pages, and wherein a result of the query is utilized to retrieve a particular page of the pages.

6. The computer system as recited in claim 1, wherein in response to receiving the particular page, the controller is configured to use the given key to identify a mapping within the particular page, the mapping including an identification of a location of a data item stored in the storage medium that corresponds to the given key.

7. The computer system as recited in claim 1, wherein the data storage controller is further configured to:

create a new level to be added to the plurality of levels, in response to detecting a condition for inserting one or more new entries in the mapping table; and

insert the one or more new entries in the new level.

8. The computer system as recited in claim 1, wherein each of the mapping table entries further comprise an indication as to where the user data corresponding to a given key is stored on a data storage medium.

9. The computer system as recited in claim 8, wherein the data storage medium comprises one or more solid state storage devices.

10. The computer system as recited in claim 1, wherein all levels of the plurality of the time ordered levels other than a youngest level are read only.

11. The computer system as recited in claim 1, further comprising an overlay table that overlays the mapping table, wherein the overlay table and mapping table are indexed by different keys.

12. The computer system as recited in claim 11, wherein the overlay table identifies one or more tuples in the mapping table that are not valid.

13. The computer system as recited in claim 11, wherein the overlay table contains one or more entries that correspond to a range of values.

14. The computer system as recited in claim 11, wherein the entry in the overlay table can be used to modify one or fields in a tuple returned from the mapping table in response to a query.

15. The computer system as recited in claim 11, wherein the key used to index the overlay table is generated from fields in the key used to access the mapping table.

16. The computer system as recited in claim 11, wherein the key used to index the overlay table is generated from fields in the tuple resulting from accessing the mapping table.

17. The computer system as recited in claim 11, further comprising a cache configured to store a cached copy of at least a portion of the overlay table.

18. The computer system as recited in claim 11, wherein the overlay table is organized as a plurality of time ordered levels, each level comprising one or more overlay table entries.

19. A method for use in a storage system, the method comprising:

storing a mapping table that includes a plurality of entries, each of the mapping table entries comprising a tuple including a key; and

storing a mapping table index that includes a plurality of entries;

wherein the mapping table is organized as a plurality of time ordered levels, each level comprising one or more mapping table entries.

20. The method as recited in claim 19, wherein in response to receiving the particular page, the method further comprises using the given key to identify a mapping within the particular page, the mapping including an identification of a location of a data item stored in the storage medium that corresponds to the given key.

21. The method as recited in claim 20, further comprising storing a cached copy of at least a portion of the mapping table.

22. The method as recited in claim 20, wherein in response to receiving a request, the method further comprises:

accessing the mapping table with at least a given key corresponding to the request;

identifying one or more entries that correspond to the given key;

determining which of the one or more entries corresponds to a youngest level of the time ordered levels; and

returning an entry that corresponds to a youngest level of the time ordered levels to satisfy the request.

23. The method as recited in claim 22, further comprising sorting each level by tuple key value.

24. The method as recited in claim 23, wherein entries of the mapping table stored in a storage medium are grouped into pages, and wherein a result of the query is utilized to retrieve a particular page of the pages.

25. The method as recited in claim 19, further comprising:

creating a new level to be added to the plurality of levels, in response to detecting a condition for inserting one or more new entries in the mapping table; and

inserting the one or more new entries in the new level.

26. The method as recited in claim 19, wherein each of the mapping table entries further comprise an indication as to where the user data corresponding to a given key is stored on a data storage medium.

27. The method as recited in claim 26, wherein the data storage medium comprises one or more solid state storage devices.

28. The method as recited in claim 19, wherein all levels of the plurality of the time ordered levels other than a youngest level are read only.

29. The method as recited in claim 19, further comprising an overlay table that overlays the mapping table, wherein the overlay table and mapping table are indexed by different keys.

30. The method as recited in claim 29, wherein the overlay table identifies one or more tuples in the mapping table that are not valid.

31. The method as recited in claim 29, wherein the overlay table contains one or more entries that correspond to a range of values.

32. The method as recited in claim 29, further comprising using the entry in the overlay table to modify one or fields in a tuple returned from the mapping table in response to a query.

33. The method as recited in claim 29, wherein the key used to index the overlay table is generated from fields in the key used to access the mapping table.

34. The method as recited in claim 29, wherein the key used to index the overlay table is generated from fields in the tuple resulting from accessing the mapping table.

35. A non-transitory computer readable storage medium storing program instruction executable by a processor to:

store a mapping table that includes a plurality of entries, each of the mapping table entries comprising a tuple including a key; and

store a mapping table index that includes a plurality of entries;

wherein the mapping table is organized as a plurality of time ordered levels, each level comprising a plurality of mapping table entries.

36. The computer readable storage medium as recited in claim 35, wherein the program instructions are further executable to store in a cache a cached copy of at least a portion of the mapping table index.

37. The computer readable storage medium as recited in claim 35, wherein the program instructions are further executable to sort the cached copy by tuple key value.