Managing mapping information in a storage system

• US 10,254,964 B1
• Filed: 04/30/2018
• Issued: 04/09/2019
• Est. Priority Date: 11/24/2014
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Pure Storage, Inc.
• Inventors: Sanvido, Marco, Hankins, Richard, McAuliffe, Mark, Vachharajani, Neil
• Primary Examiner(s): Queler, Adam M
• Assistant Examiner(s): Kwong, Edmund H
• Application Number:
  US15/966,036
• Time in Patent Office: 344 Days
• Field of Search: None
• CPC Class Codes: G06F 12/023 Free address space management
• CPC Class Codes: G06F 12/0238 Memory management in non-volatile memory, e.g. resistive RAM or ferroelectric memory
• CPC Class Codes: G06F 12/0292 using tables or multilevel address translation means G06F12/023 takes precedence; address translation in virtual memory systems G06F12/10
• CPC Class Codes: G06F 12/121 using replacement algorithms
• CPC Class Codes: G06F 2212/401 Compressed data
• 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 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0641 De-duplication techniques
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A system and method for efficiently maintaining metadata stored among 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 at least pairs of a key value and a physical pointer value. The levels are sorted by time. New records are inserted in a created new highest (youngest) level. No edits are performed in-place. A data storage controller determines both a cost of searching a given table exceeds a threshold and an amount of memory used to flatten levels exceeds a threshold. In response, the controller incrementally flattens selected levels within the table based on key ranges. After flattening the records in the selected levels within the key range, the records may be removed from the selected levels. The process repeats with another different key range.

Claims

1. A node-based storage cluster, the node-based storage cluster configured to:

detect a condition for flattening two or more levels within a multi-level data structure that includes a plurality of levels, wherein the condition includes a time needed to search multiple levels in a mapping table exceeding a threshold; and

responsive to detecting the condition;

select two or more levels for flattening;

determine a key range with each of the two or more levels that is smaller than a complete level for incremental flattening;

create a subset of a new level to be added to the multi-level data structure, wherein the new level includes all valid entries from the key range in the two or more levels;

receive, from each node in the node-based storage cluster, verification that the node is ready to utilize the new level; and

remove, from the node-based storage cluster, the key range of the two or more levels for incremental flattening, including archiving the key range of the two or more levels for incremental flattening in offline storage.

2. The node-based storage cluster of claim 1 wherein each level includes one or more entries and each entry within a level is associated with a key that is unique from all other entries in the level.

3. The node-based storage cluster of claim 1, wherein the node-base storage cluster is further configured to:

insert, within the new level, each entry in the two or more levels whose key does not match the key of any other entry in the two or more levels; and

insert, within the new level, each valid entry in the two or more levels whose key does match the key of another entry in the two or more levels.

4. The node-based storage cluster of claim 1 wherein the plurality of levels are organized based on temporal relationships between the levels.

5. The node-based storage cluster of claim 1 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is valid if the entry is included within a more recent level than any other entries in the two or more levels that are associated with the same key.

6. The node-based storage cluster of claim 1 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is invalid if the entry is included within a less recent level than any other entries in the two or more levels that are associated with the same key.

7. The node-based storage cluster of claim 1 wherein the node-based storage cluster is further configured to select the two or more levels based at least in part on an age of the two or more levels relative to other levels in the multi-level data structure.

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

detecting a condition for flattening two or more levels within a multi-level data structure that includes a plurality of levels, wherein the condition includes a time needed to search multiple levels in a mapping table exceeding a threshold; and

responsive to detecting the condition;

selecting two or more levels for flattening;

determining a key range with each of the two or more levels that is smaller than a complete level for incremental flattening;

creating a subset of a new level to be added to the multi-level data structure, wherein the new level includes all valid entries from the key range in the two or more levels;

receiving, from each node in the node-based storage cluster, verification that the node is ready to utilize the new level; and

removing, from the node-based storage cluster, the key range of the two or more levels for incremental flattening, including archiving the key range of the two or more levels for incremental flattening in offline storage.

9. The method of claim 8 wherein each level includes one or more entries and each entry within a level is associated with a key that is unique from all other entries in the level.

10. The method of claim 8 further comprising:

inserting, within the new level, each entry in the two or more levels whose key does not match the key of any other entry in the two or more levels; and

inserting, within the new level, each valid entry in the two or more levels whose key does match the key of another entry in the two or more levels.

11. The method of claim 8 wherein the plurality of levels are organized based on temporal relationships between the levels.

12. The method of claim 8 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is valid if the entry is included within a more recent level than any other entries in the two or more levels that are associated with the same key.

13. The method of claim 8 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is invalid if the entry is included within a less recent level than any other entries in the two or more levels that are associated with the same key.

14. The method of claim 8 further comprising selecting the two or more levels based at least in part on an age of the two or more levels relative to other levels in the multi-level data structure.

15. An apparatus for use in a storage system that includes a plurality of storage devices, the apparatus including a computer processor and a computer memory, the computer memory including computer program instructions that, when executed by the computer processor, cause the storage system to carry out the steps of:

detecting a condition for flattening two or more levels within a multi-level data structure that includes a plurality of levels, wherein the condition includes a time needed to search multiple levels in a mapping table exceeding a threshold; and

responsive to detecting the condition;

selecting two or more levels for flattening;

determining a key range with each of the two or more levels that is smaller than a complete level for incremental flattening;

creating a subset of a new level to be added to the multi-level data structure, wherein the new level includes all valid entries from the key range in the two or more levels;

receiving, from each node in the node-based storage cluster, verification that the node is ready to utilize the new level; and

removing, from the node-based storage cluster, the key range of the two or more levels for incremental flattening, including archiving the key range of the two or more levels for incremental flattening in offline storage.

16. The apparatus of claim 15 wherein each level includes one or more entries and each entry within a level is associated with a key that is unique from all other entries in the level.

17. The apparatus of claim 15 further comprising computer program instructions that, when executed by the computer processor, cause the storage system to carry out the steps of:

inserting, within the new level, each entry in the two or more levels whose key does not match the key of any other entry in the two or more levels; and

inserting, within the new level, each valid entry in the two or more levels whose key does match the key of another entry in the two or more levels.

18. The apparatus of claim 15 wherein the plurality of levels are organized based on temporal relationships between the levels.

19. The apparatus of claim 15 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is valid if the entry is included within a more recent level than any other entries in the two or more levels that are associated with the same key.

20. The apparatus of claim 15 wherein the entry in the two or more levels whose key does match the key of another entry in the two or more levels is invalid if the entry is included within a less recent level than any other entries in the two or more levels that are associated with the same key.