ADAPTIVE RAID FOR AN SSD ENVIRONMENT

• US 20140317447A1
• Filed: 05/21/2014
• Published: 10/23/2014
• Est. Priority Date: 09/28/2010
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Pure Storage, Inc.
• Inventors: Colgrove, John, Hayes, John, Hong, Bo, Miller, Ethan
• Granted Patent: US 9,594,633 B2
• Time in Patent Office: Days
• US Class Current: 714/6.24
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 11/2053 where persistent mass storage functionality or persistent mass storage control functionality is redundant error detection or correction in information storage based on relative movement between record carrier and transducer G11B20/18
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0646 Horizontal data movement in storage systems, i.e. moving data in between storage devices or systems
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A system and method for adaptive RAID geometries. A computer system comprises client computers and data storage arrays coupled to one another via a network. A data storage array utilizes solid-state drives and Flash memory cells for data storage. A storage controller within a data storage array is configured to determine a first RAID layout for use in storing data, and write a first RAID stripe to the device group according to the first RAID layout. In response to detecting a first condition, the controller is configured to determine a second RAID layout which is different from the first RAID layout, and write a second RAID stripe to the device group according to the second layout, whereby the device group concurrently stores data according to both the first RAID layout and the second RAID layout.

Claims

1. A computer system comprising:

a client computer configured to send read and write requests over a network;

a data storage subsystem coupled to the network configured to receive the read and write requests, wherein the subsystem comprises a plurality of data storage locations on a device group including a plurality of storage devices;

wherein the data storage subsystem further comprises a storage controller configured to;

determine a first RAID layout for use in storing data;

write a first RAID stripe to the device group according to the first RAID layout; and

in response to detecting a first condition;

determine a second RAID layout which is different from the first RAID layout, said second RAID layout being determined without regard to an amount of data to be written; and

write a second RAID stripe to the device group according to the second layout;

whereby the device group concurrently stores data according to both the first RAID layout and the second RAID layout.

2. The computer system as recited in claim 1, wherein said condition comprises detecting space is to be allocated for storing data in the device group.

3. The computer system as recited in claim 1, wherein the storage controller is configured to determine the first RAID layout and the second RAID layout based upon characteristics of one or more of the plurality of storage devices.

4. The computer system as recited in claim 3, wherein the characteristics include one or more of a number or rate of accesses to one or more of the plurality of devices, an age of data stored in one or more of the plurality of devices, an amount of free space in one or more of the plurality of storage devices, an expected life of data to be written in the space allocated, an expected life of data currently stored in one or more of the plurality of storage devices, a device age, an error rate, a number of errors, a number of recoverable errors, a number of unrecoverable errors, and an allocation state.

5. The computer system as recited in claim 1, wherein the storage controller is further configured to shred protection data in the plurality of storage devices, whereby the storage controller is configured to at least:

determine a level of protection for given data is to be changed;

identify particular storage locations storing protection data corresponding to the given data; and

de-allocate the particular storage locations.

6. The computer system as recited in claim 5, wherein the storage controller is further configured to reallocate one or more of the particular storage locations for storing non-protection data during a subsequent write.

7. The computer system as recited in claim 6, wherein a reallocated particular storage location need not use a same size or alignment for the non-protection data as was used for the protection data.

8. The computer system as recited in claim 1, wherein a storage device of the plurality of storage devices is configured to erase data in erase block size units, and wherein in response to detecting an access to a portion of data smaller in size than an erase block has failed, the storage controller is configured to:

identify a particular erase block sized portion of data that includes the portion of data that failed;

rebuild the portion of data that failed to form a rebuilt portion of data; and

cause the storage device to write the particular erase block sized portion of data including the rebuilt portion of data.

9. The computer system as recited in claim 1, wherein in response to detecting an access to a portion of data has failed, the storage controller is configured to:

rebuild the portion of data that failed to form a rebuilt portion of data;

shred protection data in a particular storage device of the plurality of storage devices; and

store the rebuilt portion of data in the particular storage location.

10. The computer system as recited in claim 1, wherein the storage controller is further configured to issue a command to a storage device of the plurality of storage devices which causes the storage device to remap and rewrite a portion of data stored in the storage device.

11. A method for use in a computer system, the method comprising:

receiving read and write requests at a data storage subsystem, wherein the subsystem comprises a plurality of data storage locations on a device group including a plurality of storage devices;

determining a first RAID layout for use in storing data;

writing a first RAID stripe to the device group according to the first RAID layout; and

in response to detecting a first condition;

determining a second RAID layout which is different from the first RAID layout, said second RAID layout being determined without regard to an amount of data to be written; and

writing a second RAID stripe to the device group according to the second layout;

whereby the device group concurrently stores data according to both the first RAID layout and the second RAID layout.

12. The method as recited in claim 11, wherein said condition comprises detecting space is to be allocated for storing data in the device group.

13. The method as recited in claim 11, further comprising determining the first RAID layout and the second RAID layout based upon characteristics of one or more of the plurality of storage devices.

14. The method as recited in claim 13, wherein the characteristics include one or more of a number or rate of accesses to one or more of the plurality of devices, an age of data stored in one or more of the plurality of devices, an amount of free space in one or more of the plurality of storage devices, an expected life of data to be written in the space allocated, an expected life of data currently stored in one or more of the plurality of storage devices, a device age, an error rate, a number of errors, a number of recoverable errors, a number of unrecoverable errors, and an allocation state.

15. The method as recited in claim 11, further comprising shredding protection data in the plurality of storage devices, whereby the method comprises:

determining a level of protection for given data is to be changed;

identifying particular storage locations storing protection data corresponding to the given data; and

de-allocating the particular storage locations.

16. The method as recited in claim 15, reallocating one or more of the particular storage locations for storing non-protection data during a subsequent write.

17. The method as recited in claim 16, wherein a reallocated particular storage location need not use a same size or alignment for the non-protection data as was used for the protection data.

18. The method as recited in claim 11, wherein a storage device of the plurality of storage devices is configured to erase data in erase block size units, and wherein in response to detecting an access to a portion of data smaller in size than an erase block has failed, the method further comprises:

identifying a particular erase block sized portion of data that includes the portion of data that failed;

rebuilding the portion of data that failed to form a rebuilt portion of data; and

causing the storage device to write the particular erase block sized portion of data including the rebuilt portion of data.

19. A computer readable storage medium storing program instructions, wherein the program instructions are executable to:

receive read and write requests at a data storage subsystem, wherein the subsystem comprises a plurality of data storage locations on a device group including a plurality of storage devices;

determine a first RAID layout for use in storing data;

write a first RAID stripe to the device group according to the first RAID layout; and

in response to detecting a first condition;

determine a second RAID layout which is different from the first RAID layout, said second RAID layout being determined without regard to an amount of data to be written; and

write a second RAID stripe to the device group according to the second layout;

whereby the device group concurrently stores data according to both the first RAID layout and the second RAID layout.

20. The computer readable storage medium as recited in claim 19, wherein said condition comprises detecting space is to be allocated for storing data in the device group.