STORING RAID DATA AS ENCODED DATA SLICES IN A DISPERSED STORAGE NETWORK

• US 20140351631A1
• Filed: 08/13/2014
• Published: 11/27/2014
• Est. Priority Date: 02/27/2010
• Status: Active Grant

• Current Assignee: Broadcom Corporation (Broadcom, Inc.), Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Grube, Gary W., Resch, Jason K.
• Granted Patent: US 9,116,832 B2
• Time in Patent Office: Days
• US Class Current: 714/6.23
• 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 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• 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 2211/1028 Distributed, i.e. distributed RAID systems with parity
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• 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 3/068 Hybrid storage device
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• 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]

Abstract

A method begins by a processing module receiving data for storage and interpreting the data to identify the data as redundant array of independent disks (RAID) data. The method continues with the processing module interpreting the RAID data to identify at least one of RAID block data and RAID parity data. When the RAID data includes RAID block data and RAID parity data the method continues with the processing module encoding the RAID block data in accordance with error coding dispersal storage function parameters to produce at least one set of encoded data slices and outputting the at least one set of encoded data slices to a dispersed storage network memory.

Claims

1. A method for execution by a processing module in a distributed storage (DS) unit, the method comprising:

receiving a request to retrieve data;

identifying a set of redundant array of independent disks (RAID) data blocks and corresponding RAID parity blocks that correspond to the data within RAID memory;

when the set of RAID data blocks is error-free;

retrieving the data based on the set of RAID data blocks; and

outputting, via a communication interface of the DS unit, the data based on the set of RAID data blocks; and

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

retrieving the data based on a backup copy of the data from a dispersed storage network (DSN) memory, wherein the backup copy of the data is stored in the DSN memory as one or more sets of encoded data slices; and

outputting, via the communication interface of the DS unit, the data based on the backup copy of the data.

2. The method of claim 1 further comprising:

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

generating a copy of the set of RAID data blocks based on the backup copy of the data; and

outputting, via the communication interface of the DS unit, the copy of the set of RAID data blocks.

3. The method of claim 1 further comprising:

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

generating a copy of the set of RAID data blocks based on the backup copy of the data; and

transmitting, via the communication interface of the DS unit, a store command accompanied with the copy of the set of RAID data blocks to the RAID memory.

4. The method of claim 1, wherein:

other data is stored within the DSN memory based on first distributed data storage parameters; and

the backup copy of the data is stored within the DSN memory based on second distributed data storage parameters that are relatively less reliable or have relatively less error correcting capability than the first distributed data storage parameters.

5. The method of claim 1 further comprising:

calculating other RAID parity blocks based on the set of RAID data blocks;

comparing the other RAID parity blocks with the RAID parity blocks;

determining that the set of RAID data blocks is error-free when the other RAID parity blocks compare favorably with the RAID parity blocks; and

determining that the set of RAID data blocks includes one or more errors when the other RAID parity blocks compare unfavorably with the RAID parity blocks.

6. The method of claim 1 further comprising:

when the set of RAID data blocks includes the more errors than are correctable based on the RAID parity blocks;

retrieving a decode threshold number of error coded (EC) data slices of a set of EC data slices from the DSN memory, wherein a data segment of the backup copy of the data is dispersed error encoded to produce the set of EC data slices;

reconstructing the data segment of the backup copy of the data using the decode threshold number of EC data slices; and

reconstructing the backup copy of the data using the data segment.

7. The method of claim 1, wherein the DSN memory is local DSN memory that is located within local proximity to the DS unit.

8. The method of claim 1, wherein the DSN memory is remote DSN memory that is included within another at least one DS unit that is located outside of local proximity to the DS unit.

9. A distributed storage (DS) processing unit comprises:

a communication interface; and

a processing module configured to;

receive a request to retrieve data;

identify a set of redundant array of independent disks (RAID) data blocks and corresponding RAID parity blocks that correspond to the data within RAID memory; and

when the set of RAID data blocks is error-free;

retrieve the data based on the set of RAID data blocks; and

output, via the communication interface, the data based on the set of RAID data blocks; and

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

retrieve the data based on a backup copy of the data from a dispersed storage network (DSN) memory, wherein the backup copy of the data is stored in the DSN memory as one or more sets of encoded data slices; and

output, via the communication interface, the data based on the backup copy of the data.

10. The DS processing unit of claim 9, wherein the processing module is further configured, when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks, to:

generate a copy of the set of RAID data blocks based on the backup copy of the data; and

output, via the communication interface of the DS unit, the copy of the set of RAID data blocks.

11. The DS processing unit of claim 9, wherein the processing module is further configured, when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks, to:

generate a copy of the set of RAID data blocks based on the backup copy of the data; and

transmit, via the communication interface of the DS unit, a store command accompanied with the copy of the set of RAID data blocks to the RAID memory.

12. The DS processing unit of claim 9, wherein:

other data is stored within the DSN memory based on first distributed data storage parameters; and

the backup copy of the data is stored within the DSN memory based on second distributed data storage parameters that are relatively less reliable or have relatively less error correcting capability than the first distributed data storage parameters.

13. The DS processing unit of claim 9, wherein the processing module is further configured to:

calculate other RAID parity blocks based on the set of RAID data blocks;

compare the other RAID parity blocks with the RAID parity blocks;

determine that the set of RAID data blocks is error-free when the other RAID parity blocks compare favorably with the RAID parity blocks; and

determine that the set of RAID data blocks includes one or more errors when the other RAID parity blocks compare unfavorably with the RAID parity blocks.

14. The DS processing unit of claim 9, wherein the processing module is further configured, when the set of RAID data blocks includes the more errors than are correctable based on the RAID parity blocks, to:

retrieve a decode threshold number of error coded (EC) data slices of a set of EC data slices from the DSN memory, wherein a data segment of the backup copy of the data is dispersed error encoded to produce the set of EC data slices;

reconstruct the data segment of the backup copy of the data using the decode threshold number of EC data slices; and

reconstruct the backup copy of the data using the data segment.

15. The DS processing unit of claim 9, wherein the DSN memory is local DSN memory that is located within local proximity to the DS unit.

16. The DS processing unit of claim 9, wherein the DSN memory is remote DSN memory that is included within another at least one DS unit that is located outside of local proximity to the DS unit.

17. A computer readable medium having instructions causing a processing module in a distributed storage (DS) unit to execute a method comprising:

receiving a request to retrieve data;

identifying a set of redundant array of independent disks (RAID) data blocks and corresponding RAID parity blocks that correspond to the data within RAID memory;

when the set of RAID data blocks is error-free;

retrieving the data based on the set of RAID data blocks; and

outputting, via a communication interface of the DS unit, the data based on the set of RAID data blocks; and

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

retrieving the data based on a backup copy of the data from a dispersed storage network (DSN) memory, wherein the backup copy of the data is stored in the DSN memory as one or more sets of encoded data slices; and

outputting, via the communication interface of the DS unit, the data based on the backup copy of the data.

18. The computer readable medium having instructions causing the processing module to execute the method of claim 17 further comprising:

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

generating a copy of the set of RAID data blocks based on the backup copy of the data; and

outputting, via the communication interface of the DS unit, the copy of the set of RAID data blocks.

19. The computer readable medium having instructions causing the processing module to execute the method of claim 17 further comprising:

when the set of RAID data blocks includes more errors than are correctable based on the RAID parity blocks;

generating a copy of the set of RAID data blocks based on the backup copy of the data; and

transmitting, via the communication interface of the DS unit, a store command accompanied with the copy of the set of RAID data blocks to the RAID memory.

20. The computer readable medium having instructions causing the processing module to execute the method of claim 17, wherein:

other data is stored within the DSN memory based on first distributed data storage parameters; and

the backup copy of the data is stored within the DSN memory based on second distributed data storage parameters that are relatively less reliable or have relatively less error correcting capability than the first distributed data storage parameters.

21. The computer readable medium having instructions causing the processing module to execute the method of claim 17 further comprising:

calculating other RAID parity blocks based on the set of RAID data blocks;

comparing the other RAID parity blocks with the RAID parity blocks;

determining that the set of RAID data blocks is error-free when the other RAID parity blocks compare favorably with the RAID parity blocks; and

determining that the set of RAID data blocks includes one or more errors when the other RAID parity blocks compare unfavorably with the RAID parity blocks.

22. The computer readable medium having instructions causing the processing module to execute the method of claim 17 further comprising:

when the set of RAID data blocks includes the more errors than are correctable based on the RAID parity blocks;

retrieving a decode threshold number of error coded (EC) data slices of a set of EC data slices from the DSN memory, wherein a data segment of the backup copy of the data is dispersed error encoded to produce the set of EC data slices;

reconstructing the data segment of the backup copy of the data using the decode threshold number of EC data slices; and

reconstructing the backup copy of the data using the data segment.

23. The computer readable medium having instructions causing the processing module to execute the method of claim 17, wherein the DSN memory is local DSN memory that is located within local proximity to the DS unit.

24. The computer readable medium having instructions causing the processing module to execute the method of claim 17, wherein the DSN memory is remote DSN memory that is included within another at least one DS unit that is located outside of local proximity to the DS unit.