Extent hashing technique for distributed storage architecture

Patent metadata

Field	Value
Publication number	US-9405783-B2
Application number	US-201314044624-A
Country	US
Kind code	B2
Filing date	Oct 2, 2013
Priority date	Oct 2, 2013
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

In one embodiment, a technique is provided for distributing data and associated metadata within a distributed storage architecture. A set of hash tables that embody mappings of cluster-wide identifiers associated with storage locations are stored for write data of write requests organized into extents. A hash value is generated from a hash function applied to each extent. The hash value is overloaded and used for multiple purposes within the distributed storage architecture, including (i) a remainder computation on the hash value to select a bucket of a plurality of buckets representative of the extents, (ii) a hash table selector of the hash value to select a hash table from the set of hash tables, and (iii) a hash table index computed from the hash value to select an entry from a plurality of entries of the selected hash table having a cluster-wide identifier identifying a storage location for the extent.

First claim

What is claimed is:

1. A system comprising:
a central processing unit (CPU) of a node of a cluster having additional nodes, each node coupled to one or more solid state drives (SSDs); and
a memory coupled to the CPU and configured to store a set of hash tables embodying mappings of cluster-wide identifiers associated with storage locations on the SSDs for write data of write requests organized into extents, the memory further configured to store a storage input/output (I/O) stack having a plurality of layers that cooperate with components of the additional nodes to provide a distributed storage architecture of the cluster, the layers of the storage I/O stack implemented as one or more processes executable by the CPU to:
generate a hash value from a hash function applied to each extent; and
overload the hash value for multiple purposes within the distributed storage architecture, including (i) a remainder computation on the hash value to select a bucket of a plurality of buckets representative of the extents, (ii) a hash table selector of the hash value to select a hash table from the set of hash tables, and (iii) a hash table index computed from the hash value to select an entry from a plurality of entries of the selected hash table having a cluster-wide identifier identifying a SSD storage location for an extent.

2. The system of claim 1 wherein overload of the hash value is achieved by applying prime divisors to the hash value.

3. The system of claim 1 wherein the hash function includes a property of block data randomization.

4. The system of claim 1 wherein the hash function includes a property that changing of bits of the extent results in each bit independently having a same chance of changing in the hash value.

5. The system of claim 1 wherein the hash function includes a distribution property that ensures the entries of the selected hash table are substantially balanced and substantially evenly accessed.

6. The system of claim 1 wherein the remainder computation is based on modulus arithmetic.

7. The system of claim 6 wherein the modulus arithmetic comprises a remainder of the hash value modulo a number of buckets.

8. A method comprising:
storing a set of hash tables that embody mappings of cluster-wide identifiers associated with storage locations on one or more solid state drives (SSDs) of a distributed storage architecture for write data of write requests organized into extents;
generating a hash value from a hash function applied to each extent; and
overloading the hash value for multiple purposes within the distributed storage architecture, including (i) a remainder computation on the hash value to select a bucket of a plurality of buckets representative of the extents, (ii) a hash table selector of the hash value to select a hash table from the set of hash tables, and (iii) a hash table index computed from the hash value to select an entry from a plurality of entries of the selected hash table having a cluster-wide identifier identifying a SSD storage location for an extent.

9. The method of claim 8 wherein overloading the hash value further comprises:
applying prime divisors to the hash value.

10. The method of claim 8 wherein the hash function includes a property of data randomization.

11. The method of claim 8 wherein the hash function includes a property that changing of bits of the extent results in each bit independently having a same chance of changing in the hash value.

12. The method of claim 8 wherein the hash function includes a distribution property that ensures the entries of the selected hash table are substantially balanced and substantially evenly accessed.

13. The method of claim 8 wherein the remainder computation is based on modulus arithmetic.

14. The method of claim 13 wherein the modulus arithmetic comprises a remainder of the hash value modulo a number of buckets.

15. A non-transitory computer readable medium including program instructions for execution on one or more processors, the program instructions when executed operable to:
store a set of hash tables that embody mappings of cluster-wide identifiers associated with storage locations on one or more solid state drives (SSDs) of a distributed storage architecture for write data of write requests organized into extents;
generate a hash value from a hash function applied to each extent; and
overload the hash value for multiple purposes within the distributed storage architecture, including (i) a remainder computation on the hash value to select a bucket of a plurality of buckets representative of the extents, (ii) a hash table selector of the hash value to select a hash table from the set of hash tables, and (iii) a hash table index computed from the hash value to select an entry from a plurality of entries of the selected hash table having a cluster-wide identifier identifying a SSD storage location for an extent.

16. The non-transitory computer readable medium of claim 15 wherein overload of the hash value is achieved by applying prime divisors to the hash value.

17. The non-transitory computer readable medium of claim 15 wherein the hash function includes a property of block data randomization.

18. The non-transitory computer readable medium of claim 15 wherein the hash function includes a property that changing of bits of the extent results in each bit independently having a same chance of changing in the hash value.

19. The non-transitory computer readable medium of claim 15 wherein the hash function includes a distribution property that ensures the entries of the selected hash table are substantially balanced and substantially evenly accessed.

20. The non-transitory computer readable medium of claim 15 wherein the remainder computation is based on modulus arithmetic.

Assignees

• Netapp Inc

Inventors

• Kimmel Jeffrey S
• Lewis Blake H

Classifications

• G06F3/0608 Primary

  Saving storage space on storage systems · CPC title

• G06F17/30097

  Physics · mapped topic

• G06F3/0641

  De-duplication techniques · CPC title

• G06F17/3033 Primary

  Physics · mapped topic

• G06F17/30949

  Physics · mapped topic