Faster rebuilding of 2-disk failure in raid by efficient, modular, diagonal, concurrent parity
In response to receiving data to be stored in a storage system that includes a plurality of N drives, a method may include storing a first quantity of the data in a first N portions across a first half of the N drives; storing a second quantity of the data in a second N portions across a second half of the N drives; determining first parities to be stored on a first parity drive; determining second parities and storing them on a second parity drive; and calculating third parities based on both the first quantity of the data and the second quantity of the data, wherein the third parities are calculated in a diagonal fashion based on distinct elements of the first N portions and distinct elements of the second N portions, and storing the third parities on a third parity drive.
1. A method comprising:
in response to receiving data to be stored in a storage system that includes a plurality of N drives, performing data storing operations comprising:
segregating the N drives into a first half and a second half;
storing a first quantity of the data in a first N/2 portions across the first half of the N drives;
storing a second quantity of the data in a second N/2 portions across the second half of the N drives;
for each of the first N/2 portions of the first quantity of the data, determining a first parity, and storing each first parity on a first parity drive;
for each of the second N/2 portions of the second quantity of the data, determining a second parity, and storing each second parity on a second parity drive,
wherein the first parity drive is operable to store only the first parities, and wherein the second parity drive is operable to store only the second parities; and
calculating third parities based on both the first quantity of the data and the second quantity of the data, wherein the third parities are calculated in a diagonal fashion based on distinct elements of the first N/2 portions and distinct elements of the second N/2 portions, and storing the third parities on a third parity drive, wherein the third parity drive is operable to store only the third parities.
2. The method of claim 1 , wherein the first, second, and third parities are calculated based on an XOR operation.
3. The method of claim 1 , wherein at least one of the first, second, and third parities are based on an XOR operation.
4. The method of claim 1 , further comprising: in response to a failure of a particular drive in the first half of the N drives, re-generating data based on the first parities.
5. The method of claim 4 , further comprising: in response to a contemporaneous failure of a second particular drive in the second half of the N drives, concurrently re-generating data based on the second parities.
6. The method of claim 5 , further comprising: in response to a contemporaneous failure of a third particular drive, re-generating data based on the third parities.
7. An article of manufacture comprising a non-transitory, computer-readable medium having instructions stored thereon that are configured to be executed by an information handling system for, in response to receiving data to be stored in a storage system that includes a plurality of N drives, performing data storing operations comprising:
segregating the N drives into a first half and a second half;
storing a first quantity of the data in a first N/2 portions across the first half of the N drives;
storing a second quantity of the data in a second N/2 portions across the second half of the N drives;
for each of the first N/2 portions of the first quantity of the data, determining a first parity, and storing each first parity on a first parity drive;
for each of the second N/2 portions of the second quantity of the data, determining a second parity, and storing each second parity on a second parity drive, wherein the first parity drive is operable to store only the first parities, and wherein the second parity drive is operable to store only the second parities; and
calculating third parities based on both the first quantity of the data and the second quantity of the data, wherein the third parities are calculated in a diagonal fashion based on distinct elements of the first N/2 portions and distinct elements of the second N/2 portions, and storing the third parities on a third parity drive, wherein the third parity drive is operable to store only the third parities.
8. The article of claim 7 , wherein the first, second, and third parities are calculated based on an XOR operation.
9. The article of claim 7 , wherein at least one of the first, second, and third parities are based on an XOR operation.
10. The article of claim 7 , wherein the instructions are further for: in response to a failure of a particular drive in the first half of the N drives, re-generating data based on the first parities.
11. The article of claim 10 , wherein the instructions are further for: in response to a contemporaneous failure of a second particular drive in the second half of the N drives, concurrently re-generating data based on the second parities.
12. The article of claim 11 , wherein the instructions are further for: in response to a contemporaneous failure of a third particular drive, re-generating data based on the third parities.
13. A system comprising:
at least one processor; and
a storage system that includes a plurality of N drives;
wherein, in response to receiving data to be stored in the storage system, the system s configured to perform data storing operations comprising:
storing a first quantity of the data n a first N/2 portions across a first half of the N drives;
storing a second quantity of the data n a second N/2 portions across a second half of the N drives;
for each of the first N/2 portions of the first quantity of the data, determining a first parity, and storing each first parity on a first parity drive;
for each of the second N/2 portions of the second quantity of the data, determining a second parity, and storing each second parity on a second parity drive, wherein the first parity drive is operable to store only the first parities, and wherein the second parity drive is operable to store only the second parities; and
calculating third parities based on both the first quantity of the data and the second quantity of the data, wherein the third parities are calculated in a diagonal fashion based on distinct elements of the first N/2 portions and distinct elements of the second N/2 portions, and storing the third parities on a third parity drive, wherein the third parity drive is operable to store only the third parities.
14. The system of claim 13 , wherein the first, second, and third parities are calculated based on an XOR operation.
15. The system of claim 13 , wherein the operations further comprise: in response to a failure of a particular drive in the first half of the N drives, re-generating data based on the first parities.
16. The system of claim 15 , wherein the operations further comprise: in response to a contemporaneous failure of a second particular drive in the second half of the N drives, concurrently re-generating data based on the second parities.
17. The system of claim 16 , wherein the operations further comprise: in response to a contemporaneous failure of a third particular drive, re-generating data based on the third parities.