DISTRIBUTED STORAGE NETWORK INCLUDING MEMORY DIVERSITY

• US 20120265937A1
• Filed: 06/21/2012
• Published: 10/18/2012
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Resch, Jason K., Gladwin, S. Christopher
• Granted Patent: US 8,862,800 B2
• Time in Patent Office: Days
• US Class Current: 711/118
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 2211/1011 Clustered RAID, i.e. clustered or de-clustered RAID where data and parity are spread over more disks than blocks in a parity group
• CPC Class Codes: G06F 3/0617 in relation to availability
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• 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 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/101 based on network conditions
• CPC Class Codes: H04L 67/1097 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]
• CPC Class Codes: H04N 21/231 Content storage operation, e.g. caching movies for short term storage, replicating data over plural servers, prioritizing data for deletion
• CPC Class Codes: H04N 21/2405 Monitoring of the internal components or processes of the server, e.g. server load allocation of resources in multiprogramming arrangements G06F9/50; performance measurement of computer activity G06F11/34
• CPC Class Codes: H04N 21/442 Monitoring of processes or resources, e.g. detecting the failure of a recording device, monitoring the downstream bandwidth, the number of times a movie has been viewed, the storage space available from the internal hard disk arrangements for monitoring broadcast services or broadcast-related services H04H60/29; arrangements for identifying or recognising characteristics with a direct linkage to broadcast information H04H60/35; monitoring of user activities for profile generation for accessing a video database G06F16/739; monitoring in wireless networks H04W24/00

Abstract

A dispersed storage (DS) unit a processing module and a plurality of hard drives. The processing module is operable to maintain states for at least some of the plurality of hard drives. The processing module is further operable to receive a memory access request regarding an encoded data slice and identify a hard drive of the plurality of hard drives based on the memory access request. The processing module is further operable to determine a state of the hard drive. When the hard drive is in a read state and the memory access request is a write request, the processing module is operable to queue the write request, change from the read state to a write state in accordance with a state transition process, and, when in the write state, perform the write request to store the encoded data slice in the hard drive.

Claims

1. A dispersed storage (DS) unit comprises:

a processing module; and

a plurality of hard drives, wherein the processing module is operable to;

maintain states for at least some of the plurality of hard drives;

receive a memory access request regarding an encoded data slice;

identify a hard drive of the plurality of hard drives based on the memory access request;

determine a state of the hard drive;

when the hard drive is in a read state and the memory access request is a write request;

queue the write request;

change from the read state to a write state in accordance with a state transition process; and

when in the write state, perform the write request to store the encoded data slice in the hard drive.

2. The DS unit of claim 1, wherein the state transition process comprises:

transition to the read state when a read queue associated with the hard drive contains one or more read requests and a write queue associated with the hard drive contains less than a high threshold number of write requests;

transition to the write state when the write queue contains at least the high threshold number of write requests; and

transition to a write with read priority state when the read queue is empty and the write queue contains less than the high threshold number of write requests.

3. The DS unit of claim 1, wherein the processing module is further operable to:

change from the read state to a write with priority read state in accordance with the state transition process; and

when in the write with priority read state, perform the write request to store the encoded data slice in the hard drive.

4. The DS unit of claim 1, wherein the processing module is further operable to:

when the hard drive is in the write state and the memory access request is a read request;

queue the read request;

change from the write state to the read state in accordance with a state transition process; and

when in the read state, perform the read request to read the encoded data slice from the hard drive.

5. The DS unit of claim 1, wherein the processing module is further operable to:

when the hard drive is in the write state and the memory access request is a read request;

retrieve other encoded data slices from other hard drives of the plurality of hard drives;

retrieve a corresponding parity data from a parity hard drive;

reconstruct the encoded data slice from the other encoded data slices and the corresponding parity data; and

fulfill the read request using the reconstructed encoded data slice.

6. The DS unit of claim 1 further comprises:

cache memory operably coupled to the processing module, wherein the cache memory includes a plurality of read queues corresponding to the plurality of hard drives and a plurality of write queues corresponding to the plurality of hard drives, wherein the processing module causes the cache memory to store incoming memory access requests in one of the plurality of read queues or one of the plurality of write queues.

7. A dispersed storage (DS) unit comprises:

a processing module; and

a plurality of hard drives, wherein the processing module is operable to;

for a hard drive of the plurality of hard drives;

monitor a read queue and a write queue;

when the read queue contains one or more read requests and the write queue contains less than a high threshold number of write requests, access the hard drive to execute a read request of the one or more read requests;

when the write queue contains at least the high threshold number of write requests, access the hard drive to execute one of the high threshold number of write requests; and

when the read queue is empty and the write queue contains less than the high threshold number of write requests, access the hard drive to execute one of the less than the high threshold number of write requests.

8. The DS unit of claim 7, wherein the processing module is further operable to:

when the write queue contains at least the high threshold number of write requests;

retrieve the read request from the read queue, wherein the read request is regarding an encoded data slice;

retrieve other encoded data slices from other hard drives of the plurality of hard drives;

retrieve a corresponding parity data from a parity hard drive;

reconstruct the encoded data slice from the other encoded data slices and the corresponding parity data; and

fulfill the read request using the reconstructed encoded data slice.

9. The DS unit of claim 7 further comprises:

cache memory operably coupled to the processing module, wherein the cache memory includes a plurality of read queues corresponding to the plurality of hard drives and a plurality of write queues corresponding to the plurality of hard drives, wherein the processing module causes the cache memory to store incoming memory access requests in one of the plurality of read queues or one of the plurality of write queues.

10. A memory device that stores operational instructions that, when performed by a dispersed storage (DS) unit, the operational instructions cause the DS unit to:

maintain states for at least some of a plurality of hard drives associated with the DS unit;

receive a memory access request regarding an encoded data slice;

identify a hard drive of the plurality of hard drives based on the memory access request;

determining a state of the hard drive;

when the hard drive is in a read state and the memory access request is a write request;

queue the write request;

change from the read state to a write state in accordance with a state transition process; and

when in the write state, perform the write request to store the encoded data slice in the hard drive.

11. The memory device of claim 10, wherein the change from the read state to a write state in accordance with a state transition process further comprises:

transitioning to the read state when a read queue associated with the hard drive contains one or more read requests and a write queue associated with the hard drive contains less than a high threshold number of write requests;

transitioning to the write state when the write queue contains at least the high threshold number of write requests; and

transitioning to a write with read priority state when the read queue is empty and the write queue contains less than the high threshold number of write requests.

12. The memory device of claim 10 further comprises operational instructions that cause the DS unit to:

change from the read state to a write with priority read state in accordance with the state transition process; and

when in the write with priority read state, perform the write request to store the encoded data slice in the hard drive.

13. The memory device of claim 10 further comprises operational instructions that cause the DS unit to:

when the hard drive is in the write state and the memory access request is a read request;

queue the read request;

change from the write state to the read state in accordance with a state transition process; and

when in the read state, perform the read request to read the encoded data slice from the hard drive.

14. The memory device of claim 10 further comprises operational instructions that cause the DS unit to:

when the hard drive is in the write state and the memory access request is a read request;

retrieve other encoded data slices from other hard drives of the plurality of hard drives;

retrieve a corresponding parity data from a parity hard drive;

reconstruct the encoded data slice from the other encoded data slices and the corresponding parity data; and

fulfill the read request using the reconstructed encoded data slice.

15. The memory device of claim 10 further comprises:

cache memory that includes a plurality of read queues corresponding to the plurality of hard drives and a plurality of write queues corresponding to the plurality of hard drives, wherein further operational instructions cause the DS unit to engage the cache memory to store incoming memory access requests in one of the plurality of read queues or one of the plurality of write queues.

18. The memory device of claim 10 further comprises:

cache memory that includes a plurality of read queues corresponding to the plurality of hard drives and a plurality of write queues corresponding to the plurality of hard drives, wherein further operational instructions cause the DS unit to engage the cache memory to store incoming memory access requests in one of the plurality of read queues or one of the plurality of write queues.

16. A memory device that stores operational instructions that, when performed by a dispersed storage (DS) unit, the operational instructions cause the DS unit to:

monitor a read queue and a write queue of a hard drive of a plurality of hard drives associated with the DS unit;

when the read queue contains one or more read requests and the write queue contains less than a high threshold number of write requests, access the hard drive to execute a read request of the one or more read requests;

when the write queue contains at least the high threshold number of write requests, access the hard drive to execute one of the high threshold number of write requests; and

when the read queue is empty and the write queue contains less than the high threshold number of write requests, access the hard drive to execute one of the less than the high threshold number of write requests.

17. The memory device of claim 16 further comprises operational instructions that cause the DS unit to:

when the write queue contains at least the high threshold number of write requests;

retrieve the read request from the read queue, wherein the read request is regarding an encoded data slice;

retrieve other encoded data slices from other hard drives of the plurality of hard drives;

retrieve a corresponding parity data from a parity hard drive;

reconstruct the encoded data slice from the other encoded data slices and the corresponding parity data; and

fulfill the read request using the reconstructed encoded data slice.