Adjusting a number of dispersed storage units

• US 9,762,395 B2
• Filed: 03/03/2015
• Issued: 09/12/2017
• Est. Priority Date: 04/30/2014
• Status: Expired due to Fees

• Current Assignee: Pure Storage, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Kazi, Asimuddin, Resch, Jason K.
• Primary Examiner(s): Schell, Joseph
• Application Number:
  US14/636,860
• Publication Number:
  US 20150317196A1
• Time in Patent Office: 924 Days
• CPC Class Codes: G06F 11/07 Responding to the occurrence of a fault, e.g. fault tolerance
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/0754 by exceeding limits
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 2211/1004 Adaptive RAID, i.e. RAID system adapts to changing circumstances, e.g. RAID1 becomes RAID5 as disks fill up
• CPC Class Codes: G06F 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0653 Monitoring storage devices or systems
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays
• CPC Class Codes: H04L 63/0435 wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06
• CPC Class Codes: H04L 67/10 in which an application is distributed across nodes in the network software deployment G06F8/60; multiprogramming arrangements G06F9/46
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC

Abstract

A method begins by a processing module of a dispersed storage network (DSN) determining that a set of storage units of the DSN will be substantially used for read operations of dispersed storage error encoded data. For the set of storage units, the method continues with the processing module determining an actual level of reliability in retrieving a decode threshold number of encoded data slices per read request of a plurality of read requests. The method continues with the processing module comparing the actual reliability to a desired level of reliability in retrieving the decode threshold number of encoded data slices per read request of the plurality of read requests. When the actual reliability exceeds the desired reliability by a reconfiguration threshold, the method continues with the processing module removing one or more storage units from the set of storage units.

Claims

1. A method for execution by one or more processing modules of one or more computing devices of a dispersed storage network (DSN), the method comprises:

determining that a set of storage units of the DSN will be used for read operations of dispersed storage error encoded data; and

for the set of storage units;

determining an actual reliability that indicates a level of reliability in retrieving a decode threshold number of encoded data slices per read request of a plurality of read requests;

comparing the actual reliability to a desired reliability of the set of storage units, wherein the desired reliability indicates a desired level of reliability in retrieving the decode threshold number of encoded data slices per read request of the plurality of read requests; and

when the actual reliability exceeds the desired reliability by a reconfiguration threshold, removing one or more storage units from the set of storage units.

2. The method of claim 1, wherein the determining that the set of storage units will be used for read operations comprises one or more of:

determining that memory utilization of the set of storage units exceeds a utilization threshold;

receiving a read only command regarding the set of storage units; and

determining a number of read operations for the set of storage units is a multiple of a number of write operations for the set of storage units.

3. The method of claim 1, wherein the removing the one or more storage units comprises:

determining that the one or more storage units has an unacceptable failure rate; and

when the one or more storage units has the unacceptable failure rate, decommissioning the one or more storage units.

4. The method of claim 1, wherein the removing the one or more storage units comprises:

redeploying the one or more storage units to another set of storage units.

5. The method of claim 1, wherein the removing the one or more storage units comprises:

determining a reliability rate for each of the storage units in the set of storage units;

identifying one of the storage units as having a reliability rate below a low reliability threshold and decommissioning the one of the storage units; and

identifying a second one of the storage units as having a reliability rate above a high reliability threshold and redeploying the second one of the storage units.

6. The method of claim 1 further comprises:

updating one or more of;

a pillar width number, a write threshold number, or a read threshold number; and

maintaining the decode threshold number.

7. The method of claim 1 further comprises:

adjusting rebuilding parameters for the dispersed storage error encoded data.

8. The method of claim 1, wherein the determining the actual reliability comprises one of:

establishing the actual reliability as a ratio between an original pillar width number and the decode threshold number; and

establishing the actual reliability as a ratio between an effective pillar width number and the decode threshold number.

9. The method of claim 8, wherein the removing the one or more storage units comprises:

establishing the desired reliability as a ratio between a read threshold number and the decode threshold number; and

determining a number of storage units of the storage units to remove based on;

a difference between the read threshold number and the original pillar width number;

or

a difference between the read threshold number and the effective pillar width number.

10. A non-transitory computer readable storage medium comprises:

at least one memory section that stores operational instructions that, when executed by one or more processing modules of one or more computing devices of a dispersed storage network (DSN), causes the one or more computing devices to;

determine that a set of storage units of the DSN will be used for read operations of dispersed storage error encoded data; and

for the set of storage units;

determine an actual reliability that indicates a level of reliability in retrieving a decode threshold number of encoded data slices per read request of a plurality of read requests;

compare the actual reliability to a desired reliability of the set of storage units, wherein the desired reliability indicates a desired level of reliability in retrieving the decode threshold number of encoded data slices per read request of the plurality of read requests; and

when the actual reliability exceeds the desired reliability by a reconfiguration threshold, remove one or more storage units from the set of storage units.

11. The non-transitory computer readable storage medium of claim 10, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to determine that the set of storage units will be used for read operations by:

determining that memory utilization of the set of storage units exceeds a utilization threshold;

receiving a read only command regarding the set of storage units; and

determining a number of read operations for the set of storage units is a multiple of a number of write operations for the set of storage units.

12. The non-transitory computer readable storage medium of claim 10, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to remove the one or more storage units by:

determining that the one or more storage units has an unacceptable failure rate; and

when the one or more storage units has the unacceptable failure rate, decommissioning the one or more storage units.

13. The non-transitory computer readable storage medium of claim 10, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to remove the one or more storage units by:

redeploying the one or more storage units to another set of storage units.

14. The non-transitory computer readable storage medium of claim 10, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to remove the one or more storage units by:

determining a reliability rate for each of the storage units in the set of storage units;

identifying one of the storage units as having a reliability rate below a low reliability threshold and decommissioning the one of the storage units; and

identifying a second one of the storage units as having a reliability rate above a high reliability threshold and redeploying the second one of the storage units.

15. The non-transitory computer readable storage medium of claim 10 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

update one or more of;

a pillar width number, a write threshold number, or a read threshold number; and

maintain the decode threshold number.

16. The non-transitory computer readable storage medium of claim 10 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

adjust rebuilding parameters for the dispersed storage error encoded data.

17. The non-transitory computer readable storage medium of claim 10, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to determine the actual reliability by one of:

establishing the actual reliability as a ratio between an original pillar width number and the decode threshold number; and

establishing the actual reliability as a ratio between an effective pillar width number and the decode threshold number.

18. The non-transitory computer readable storage medium of claim 17, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to remove the one or more storage units by:

establishing the desired reliability as a ratio between a read threshold number and the decode threshold number; and

determining a number of storage units of the storage units to remove based on;

a difference between the read threshold number and the original pillar width number;

or

a difference between the read threshold number and the effective pillar width number.

19. A computing device of a group of computing devices of a dispersed storage network (DSN), the computing device comprises:

an interface;

a local memory; and

a processing module including a processor operably coupled to the interface and the local memory, wherein the processor functions to;

determine that a set of storage units of the DSN will be used for read operations of dispersed storage error encoded data; and

for the set of storage units;

determine an actual reliability that indicates a level of reliability in retrieving a decode threshold number of encoded data slices per read request of a plurality of read requests;

compare the actual reliability to a desired reliability of the set of storage units, wherein the desired reliability indicates a desired level of reliability in retrieving the decode threshold number of encoded data slices per read request of the plurality of read requests; and

when the actual reliability exceeds the desired reliability by a reconfiguration threshold, remove one or more storage units from the set of storage units.

20. The computing device of claim 19, wherein the processing module functions to determine that the set of storage units will be used for the read operations by:

determining that memory utilization of the set of storage units exceeds a utilization threshold;

receiving, via the interface, a read only command regarding the set of storage units; and

determining a number of read operations for the set of storage units is a multiple of a number of write operations for the set of storage units.

21. The computing device of claim 19, wherein the processing module functions to remove the one or more storage units by:

determining that the one or more storage units has an unacceptable failure rate; and

when the one or more storage units has the unacceptable failure rate, decommissioning the one or more storage units.

22. The computing device of claim 19, wherein the processing module functions to remove the one or more storage units by:

redeploying the one or more storage units to another set of storage units.

23. The computing device of claim 19, wherein the processing module functions to remove the one or more storage units by:

determining a reliability rate for each of the storage units in the set of storage units;

identifying one of the storage units as having a reliability rate below a low reliability threshold and decommissioning the one of the storage units; and

identifying a second one of the storage units as having a reliability rate above a high reliability threshold and redeploying the second one of the storage units.

24. The computing device of claim 19, wherein the processing module further functions to:

update one or more of;

a pillar width number, a write threshold number, or a read threshold number; and

maintain the decode threshold number.

25. The computing device of claim 19, wherein the processing module further functions to:

adjust rebuilding parameters for the dispersed storage error encoded data.

26. The computing device of claim 19, wherein the processing module functions to determine the actual reliability by one of:

establishing the actual reliability as a ratio between an original pillar width number and the decode threshold number; and

establishing the actual reliability as a ratio between an effective pillar width number and the decode threshold number.