Control plane method and apparatus for providing erasure code protection across multiple storage devices

• US 10,255,134 B2
• Filed: 03/27/2017
• Issued: 04/09/2019
• Est. Priority Date: 01/20/2017
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Olarig, Sompong Paul, Schwaderer, David, Kachare, Ramdas P.
• Primary Examiner(s): Contino, Paul
• Application Number:
  US15/470,774
• Publication Number:
  US 20180210785A1
• Time in Patent Office: 743 Days
• 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 11/1084 Degraded mode, e.g. caused by single or multiple storage removals or disk failures
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 11/1096 Parity calculation or recalculation after configuration or reconfiguration of the system
• CPC Class Codes: G06F 11/201 between storage system components
• CPC Class Codes: G06F 11/2012 and using different communication protocols

Abstract

A system and method for providing erasure code protection across multiple storage devices. A data switch in a storage system connects a plurality of storage devices to a remote host. Each storage device is also connected to a controller, e.g., a baseboard management controller. During normal operation, read and write commands from the remote host are sent to respective storage devices through the data switch. When a write command is executed, the storage device executing the command sends a copy of the data to the controller, which generates and stores erasure codes, e.g., on a storage device that is dedicated to the storage of erasure codes, and invisible to the remote host. When a device fails or is removed, the controller reconfigures the data switch to redirect all traffic addressed to the failed or absent storage device to the controller, and the controller responds to host commands in its stead.

Claims

1. A storage system having a storage interface, the system comprising:

a plurality of storage devices, configured to store erasure codes sufficient to recover data stored on any one of the plurality of storage devices from data on the other storage devices;

a data switch, configured during normal operation to route storage commands received through the storage interface to respective ones of the plurality of storage devices, according to a respective address in each storage command; and

a controller,

the controller being configured, in the event of failure or absence of any storage device of the plurality of storage devices;

to reconfigure the data switch to route storage commands addressed to the failed or absent storage device to the controller; and

to send, in response to each received storage command, the same command response, through the data switch and through the storage interface, as the failed or absent device would have sent were it present and operating correctly.

2. The system of claim 1, wherein each of the storage devices is configured, during normal operation, upon receipt of a write command including a data block, to store the data block and to send a copy of the data block to the controller.

3. The system of claim 2, wherein the controller is configured, upon receipt of a copy of a data block from a first storage device of the plurality of storage devices, to generate erasure codes sufficient to recover the data block, and to store the erasure codes on one or more storage devices other than the first storage device, from among the plurality of storage devices.

4. The system of claim 1, wherein a first storage device of the plurality of storage devices is configured, during normal operation, upon receipt of a write command including a data block:

to store the data block;

to generate erasure codes sufficient to recover the data block; and

to store the erasure codes on one or more storage devices other than the first storage device, from among the plurality of storage devices.

5. The system of claim 1, wherein:

a first storage device of the plurality of storage devices is configured to store erasure codes; and

the data switch is configured, during normal operation, to route each storage command received through the storage interface to a respective storage device of a subset of the plurality of storage devices, according to a respective address in the storage command, the first storage device not being a member of the subset.

6. The system of claim 1, wherein the controller is configured, in the event of failure or absence of any one of the plurality of storage devices, in response to a received read command requesting a data block:

to read erasure codes from the present and correctly operating storage devices of the plurality of storage devices;

to recover the data block; and

to send the recovered data block through the data switch and through the storage interface as part of a command response.

7. The system of claim 1, wherein:

each of the storage devices comprises a connector having a presence pin, the presence pin being connected to a respective sensing pin of the controller; and

the controller is configured to detect removal of any one of the storage devices by a change in a voltage or current at the respective sensing pin.

8. The system of claim 1, wherein the data switch is an Ethernet switch.

9. The system of claim 1, wherein the data switch has a PCIe control port, connected to a port of the controller, and the data switch is configured to receive configuration commands from the controller through the PCIe control port.

10. The system of claim 1, further comprising a PCIe switch, wherein each of the plurality of storage devices is connected to the controller through the PCIe switch.

11. The system of claim 1, wherein the controller is a baseboard management controller.

12. A method of operating a storage system having a storage interface and comprising a plurality of storage devices, a data switch, and a controller, the method comprising:

during normal operation, routing storage commands received through the storage interface to respective ones of the plurality of storage devices, according to a respective address in each storage command; and

in the event of failure or absence of any storage device of the plurality of storage devices;

reconfiguring the data switch, by the controller, to route storage commands addressed to the failed or absent storage device to the controller; and

sending, by the controller, in response to each received storage command, the same command response, through the data switch and through the storage interface, as the failed or absent device would have sent were it present and operating correctly.

13. The method of claim 12, further comprising, during normal operation, upon receipt, by a storage device of the plurality of storage devices, of a write command including a data block:

storing, by the storage device, the data block; and

sending, by the storage device, a copy of the data block to the controller.

14. The method of claim 13, further comprising, upon receipt, by the controller, of a copy of a data block from a first storage device of the plurality of storage devices:

generating, by the controller, erasure codes sufficient to recover the data block; and

storing, by the controller, the erasure codes on one or more storage devices other than the first storage device, from among the plurality of storage devices.

15. The method of claim 12, further comprising, during normal operation, upon receipt by a first storage device, of the plurality of storage devices, of a write command including a data block:

storing, by the first storage device, the data block;

generating, by the first storage device, erasure codes sufficient to recover the data block; and

storing, by the first storage device, the erasure codes on one or more storage devices other than the first storage device, from among the plurality of storage devices.

16. The method of claim 12, wherein:

a first storage device of the plurality of storage devices is configured to store erasure codes; and

the method comprises, during normal operation, routing each storage command received through the storage interface to a respective storage device of a subset of the plurality of storage devices, according to a respective address in the storage command, the first storage device not being a member of the subset.

17. The method of claim 12, wherein the system further has a PCIe switch and the controller is connected to the storage devices through the PCIe switch,

the method further comprising, in the event of failure or absence of any one of the plurality of storage devices, in response to receiving, by the controller, of a read command requesting a data block:

reading, by the controller, through the PCIe switch, erasure codes from the present and correctly operating storage devices of the plurality of storage devices;

recovering, by the controller, the data block; and

sending, by the controller, the recovered data block through the data switch and through the storage interface as part of a command response.

18. The method of claim 17, wherein each of the storage devices has a presence pin connected to a respective sensing pin of the controller;

and

the method further comprises detecting, by the controller, removal of any one of the storage devices by a change in a voltage or current at the respective sensing pin.

19. A storage system having a storage interface, the system comprising:

a plurality of storage devices, configured to store erasure codes sufficient to recover data stored on any one of the plurality of storage devices from data on the other storage devices;

a data switch, configured during normal operation to route storage commands received through the storage interface to respective ones of the plurality of storage devices, according to a respective address in each storage command; and

controlling means for, in the event of failure or absence of any storage device of the plurality of storage devices;

reconfiguring the data switch to route storage commands addressed to the failed or absent storage device to the controlling means; and

sending, in response to each received storage command, the same command response, through the data switch and through the storage interface, as the failed or absent device would have sent were it present and operating correctly.

20. The system of claim 19, wherein each of the storage devices is configured, during normal operation, upon receipt of a write command including a data block, to store the data block and to send a copy of the data block to the controlling means.