Providing resiliency to a raid group of storage devices

Patent metadata

Field	Value
Publication number	US-10013323-B1
Application number	US-201514868577-A
Country	US
Kind code	B1
Filing date	Sep 29, 2015
Priority date	Sep 29, 2015
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A technique is directed to providing resiliency to a redundant array of independent disk (RAID) group which includes multiple storage devices. The technique involves operating the RAID group in a normal state in which each storage device is (i) initially online to perform write and read operations and (ii) configured to go offline in response to a respective media error count for that storage device reaching an initial take-offline threshold. The technique further involves receiving a notification that a storage device of the RAID group has encountered a particular error situation. The technique further involves transitioning, in response to the notification, the RAID group to a high resiliency state in which each storage device that is operable is (i) still online to perform write and read operations and (ii) configured to stay online even when the respective media error count for that storage device reaches the initial take-offline threshold.

First claim

What is claimed is:

1. A computer-implemented method of providing resiliency to a redundant array of independent disk (RAID) group which includes a plurality of storage devices, the method comprising:
operating the RAID group in a normal state in which each storage device is (i) initially online to perform write and read operations and (ii) configured to go offline in response to a respective media error count for that storage device reaching an initial take-offline threshold;
receiving a notification that a storage device of the RAID group has encountered a particular error situation; and
in response to the notification, transitioning the RAID group from the normal state to a high resiliency degraded state in which each storage device that is operable is (i) still online to perform write and read operations and (ii) configured to stay online even when the respective media error count for that storage device reaches the initial take-offline threshold;
wherein receiving the notification includes electronically detecting that a first storage device of the RAID group has gone offline in response to the media error count for the first storage device reaching the initial take-offline threshold; and
wherein transitioning includes electronically preventing a second storage device of the RAID group from going offline in response to the media error count for the second storage device reaching the initial take-offline threshold,
the RAID group thereby made to operate in the high resiliency degraded state in which the second storage device remains online performing write and read operations even though the media error count of the second storage device has reached the initial take-offline threshold.

2. A computer-implemented method as in claim 1 wherein preventing includes:
configuring the second storage device to remain online regardless of a respective media error count for the second storage device.

3. A computer-implemented method as in claim 2 wherein electronically detecting includes:
receiving, as the notification, an alert indicating that the first storage device has gone offline in response to a respective media error count for the first storage device reaching the initial take-offline threshold.

4. A computer-implemented method as in claim 2 , further comprising:
receiving an alert indicating that a proactive copy operation has begun in response to an accounting for the first storage device reaching an end-of-life threshold, the proactive copy operation involving proactively copying data from the first storage device of the RAID group to a spare storage device.

5. A computer-implemented method as in claim 4 , further comprising:
proactively copying data from the first storage device of the RAID group to the spare storage device while all of the storage devices of the RAID group remain online to perform write and read operations.

6. A computer-implemented method as in claim 4 , further comprising:
reconstructing data that was not proactively copied from the first storage device of the RAID group to the spare storage device, and storing that reconstructed data on the spare storage device.

7. A computer-implemented method as in claim 2 wherein processing circuitry maintains a hierarchy of objects representing the RAID group; and wherein electronically detecting includes:
obtaining, by a RAID group object of the hierarchy, an alert indicating existence of the particular error situation, the RAID group object representing the RAID group.

8. A computer-implemented method as in claim 7 wherein electronically preventing includes:
providing a respective don't-take-offline command from the RAID group object of the hierarchy to a storage device object of the hierarchy, the storage device object of the hierarchy representing the second storage device of the RAID group.

9. A computer-implemented method as in claim 1 wherein preventing the second storage device of the RAID group from going offline includes:
sending, from processing circuitry and to the second storage device, a command that disables the second storage device from going offline in response to the media error count for the second storage device reaching the initial take-offline threshold.

10. A computer program product having a non-transitory computer readable medium which stores a set of instructions to provide resiliency to a redundant array of independent disk (RAID) group which includes a plurality of storage devices, the set of instructions, when carried out by computerized circuitry, causing the computerized circuitry to perform a method of:
operating the RAID group in a normal state in which each storage device is (i) initially online to perform write and read operations and (ii) configured to go offline in response to a respective media error count for that storage device reaching an initial take-offline threshold;
receiving a notification that a storage device of the RAID group has encountered a particular error situation; and
in response to the notification, transitioning the RAID group from the normal state to a high resiliency degraded state in which each storage device that is operable is (i) still online to perform write and read operations and (ii) configured to stay online even when the respective media error count for that storage device reaches the initial take-offline threshold;
wherein receiving the notification includes electronically detecting that a first storage device of the RAID group has gone offline in response to the media error count for the first storage device reaching the initial take-offline threshold; and
wherein transitioning includes electronically preventing a second storage device of the RAID group from going offline in response to the media error count for the second storage device reaching the initial take-offline threshold,
the RAID group thereby made to operate in the high resiliency degraded state in which the second storage device remains online performing write and read operations even though the media error count of the second storage device has reached the initial take-offline threshold.

11. A computer program product as in claim 10 wherein electronically preventing includes:
configuring the second storage device to remain online regardless of a respective media error count for the second storage device.

12. A computer program product as in claim 11 wherein electronically detecting includes:
receiving, as the notification, an alert indicating that the first storage device has gone offline in response to a respective media error count for the first storage device reaching the initial take-offline threshold.

13. A computer program product as in claim 11 , further comprising:
receiving an alert indicating that a proactive copy operation has begun in response to an accounting for the first storage device reaching an end-of-life threshold, the proactive copy operation involving proactively copying data from the first storage device of the RAID group to a spare storage device.

14. A computer program product as in claim 11 wherein processing circuitry maintains a hierarchy of objects representing the RAID group; and wherein electronically detecting includes:
obtaining, by a RAID group object of the hierarchy, an alert indicating existence of the particular error situation, the RAID group object representing the RAID group.

15. A computer program product as in claim 14 wherein electronically preventing includes:
providing a respective don't-take-offline command from the RAID group object of the hierarchy to a storage device object of the hierarchy, the storage device object of the hierarc

Assignees

• Emc Corp
• Emc Ip Holding Co Llc

Inventors

• Puhov Peter
• Proulx Ronald D
• Garrett Wayne E
• Tamilarasan Ashok
• Petsching Eric

Classifications

• G06F11/0793

  Remedial or corrective actions (recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40) · CPC title

• G06F11/0727 Primary

  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 title

• G06F11/1076

  Parity data used in redundant arrays of independent storages, e.g. in RAID systems · CPC title

• G06F3/0634

  by changing the state or mode of one or more devices · CPC title

• G06F3/0619

  in relation to data integrity, e.g. data losses, bit errors · CPC title