System and method for calculating RAID 6 check codes

Claim 3

The method of claim 1 wherein said K bits of said first check symbol difference are uppermost bits thereof.

Claim 4

The method of claim 2 wherein said K uppermost bits are renumbered as K lowermost bits of said renumbered check symbol difference.

Claim 5

The method of claim 1 wherein said index K identifies a physical storage element on which data related to said first and second check symbol differences resides.

Claim 6

The method of claim 1 wherein said generator polynomial is equal to X 64 +X 4 +1.

Claim 7

The method of claim 5 wherein said index K is greater than or equal to zero and less than or equal to 59.

Claim 8

The method of claim 1 wherein said generator polynomial is equal X 32 +X 2 +1.

Claim 9

The method of claim 7 wherein said index K is greater than or equal to zero and less than or equal to 29.

Claim 10

The method of claim 1 wherein N>>D.

Claim 11

The method of claim 1 wherein said step of calculating is carried out by XORing each of said first renumbered K bits of said renumbered check symbol difference with each of another K bits starting at bit position D respectively.

Claim 12

The method of claim 1 wherein said step of renumbering is carried out by a left rotate of said first check symbol difference by K bit positions such that K most significant bits of said first check symbol difference move to K least significant bits of said renumbered check symbol difference.

Claim 13

The method of claim 1 further comprising the step of: constructing a RAID 6 storage array of no more than N-D storage devices.

Claim 14

The method of claim 1 further comprising the step of: transposing data symbols in a data stream defining said first check symbol difference to a transposition block having a transpose factor T prior to said step of renumbering.

Claim 15

The method of claim 13 wherein T is equal to the word size of a computer for performing said method.

Claim 16

The method of claim 14 wherein T=32.

Claim 17

The method of claim 14 wherein T=64.

Claim 18

The method of claim 13 wherein said step of transposing is carried out by renumbering bits of said data symbols in said data stream.

Claim 21

The system of claim 18 wherein said K bits of said first check symbol difference are uppermost bits thereof.

Claim 22

The system of claim 19 wherein said K uppermost bits are renumbered as K lowermost bits of said renumbered check symbol difference.

Claim 23

The system of claim 18 wherein said index K identifies a physical storage element on which data related to said first and second check symbol differences resides.

Claim 24

The system of claim 18 wherein said generator polynomial is equal to X 64 +X 4 +1.

Claim 25

The system of claim 22 wherein said index K is greater than or equal to zero and less than or equal to 59.

Claim 26

The system of claim 18 wherein said generator polynomial is equal X 32 +X 2 +1.

Claim 27

The system of claim 24 wherein said index K is greater than or equal to zero and less than or equal to 29.

Claim 28

The system of claim 18 wherein N>>D.

Claim 29

The system of claim 18 wherein said calculating means comprises means for XORing each of said first renumbered K bits of said renumbered check symbol difference with each of said another K bits starting at bit position D respectively.

Claim 30

The system of claim 18 wherein said renumbering means comprises means for performing a logical left rotate of said first check symbol difference by K bit positions such that K most significant bits of said first check symbol difference move to K least significant bits of said renumbered check symbol difference.

Claim 31

The system of claim 18 further comprising: means for transposing data symbols in a data stream defining said first check symbol difference to a transposition block having a transpose factor T.

Claim 32

The system of claim 29 wherein T is equal to the word size of a computer comprising said system.

Claim 33

The system of claim 30 wherein T=32.

Claim 34

The system of claim 30 wherein T=64.

Claim 35

The system of claim 29 wherein said transposing means comprises means for renumbering bits of said data symbols in said data stream.

Claim 36

The system of claim 18 comprising a a RAID 6 storage array of no more than N-D storage devices.

Claim 37

A computer system including a RAID 6 storage array comprising a plurality of physical storage devices for storing data symbols and first and second check symbols for reconstructing said data symbols thereon, said computer system further comprising a data processor for recomputing said first and second check symbols in response to changes in said data symbols, said computer system comprising: means for determining first check symbol differences in response to changes in said data symbols; means for updating said first check symbols based upon said first check symbol differences; means for establishing a generator polynomial of the form G=X N +X D +1; means for selecting an index K; means for renumbering said first check symbol differences by K bits to define renumbered check symbol differences; means for calculating a logical difference of each of said first K bits of each of said renumbered check symbol differences with each of another K bits of said renumbered check symbol differences starting at bit position D within said renumbered check symbol differences thereof forming a resultant K bits of said renumbered check symbol differences starting at bit position D; means for defining said second check symbol differences by said renumbered check symbol differences inclusive of said resultant K bits; means for updating said second check symbols based upon said second check symbol differences; means for writing said changed data symbols and said first and second check symbols to said storage array.

Claim 38

A computer system including a RAID 6 storage array comprising a plurality of physical storage devices for storing data symbols and first and second check symbols for reconstructing said data symbols thereon, said computer system further comprising a data processor for recomputing said first and second check symbols in response to changes in said data symbols, said computer system comprising: means for determining first check symbol differences in response to changes in said data symbols; means for updating said first check symbols based upon said first check symbol differences; means for establishing a generator polynomial of the form G=X N +X D +1; means for selecting an index K; means for renumbering said first check symbol differences by K bits to define renumbered check symbol differences; means for calculating a logical difference of each of said first K bits of each of said renumbered check symbol differences with each of another K bits of said renumbered check symbol differences starting at bit position D within said renumbered check symbol differences thereof forming a resultant K bits of said renumbered check symbol differences starting at bit position D; means for defining said second check symbol differences by said renumbered check symbol differences inclusive of said resultant K bits; means for updating said second check symbols based upon said second check symbol differences; means for writing said changed data symbols and said first and second check symbols to said storage array.

Claim 39

The computer system of claim 35 wherein said determining means comprises means for XORing an old data symbol with a new data symbol to determine said first check symbol difference.

Claim 40

The computer system of claim 35 wherein said first check symbol difference is a P check symbol difference within a P+Q RAID 6 implementation.

Claim 41

The computer system of claim 35 wherein said index K is related to the physical storage device of said storage array on which said data symbols reside.

Claim 42

The computer system of claim 35 wherein said second check symbol difference is a Q check symbol difference within a P+Q RAID 6 implementation.

Claim 43

The computer system of claim 35 wherein said K uppermost bits are renumbered as K lowermost bits of said renumbered check symbol differences.

Claim 44

The computer system of claim 35 wherein said generator polynomial is equal to X 64 +X 4 +1.

Claim 45

The computer system of claim 35 wherein said generator polynomial is equal X 32 +X 2 +1.

Claim 46

The computer system of claim 35 wherein N>>D.

Claim 47

The computer system of claim 35 wherein said calculating means comprises means for XORing each of said first renumbered K bits of said renumbered check symbol differences with each of said another K bits starting at bit position D respectively.

Claim 48

The computer system of claim 35 wherein said renumbering means comprises means for performing a logical left rotate of said first check symbol difference by K bit positions such that K most significant bits of said first check symbol differences move to K least significant bits of said renumbered check symbol differences.

Claim 49

The computer system of claim 35 further comprising: means for transposing data symbols in a data stream defining said first check symbol differences to transposition blocks having a transpose factor T.

Claim 50

The computer system of claim 46 wherein T is equal to the word size of said data processor.

Claim 51

The computer system of claim 47 wherein T=32.

Claim 52

The computer system of claim 47 wherein T=64.

Claim 53

The computer system of claim 46 wherein said transposing means comprises means for renumbering bits of said data symbols in said data stream.

Claim 54

The system of claim 35 comprising a a RAID 6 storage array of no more than N-D storage devices.