Application-assisted recovery from data corruption in parity RAID storage using successive re-reads
View Patent ↗An apparatus or method that tracks the identity of stripe units or group of stripe units from which data has been previously read by an application program running on a computer system. In one embodiment, the present invention stores the identity of previously read stripe units or groups of stripe units in a table. If the application program requests data of one of stripe unit or groups of stripe units whose identity is stored in the table, the requested data is regenerated from parity data and data of the stripe or stripes other than the requested data. This generated data is returned to the application program rather then the existing data stored in the stripe unit groups of stripe units.
1. In a RAID data storage system, a method comprising:
receiving a first request to read data of a first stripe unit of a stripe, wherein the first request is received from a computer system in data communication with the RAID data storage system;
returning data of the first stripe unit to the computer system in response to receiving the first request;
receiving a second request to read data of the first stripe unit, wherein the second request is received from the computer system;
generating reconstructed data for the first stripe unit in response to receiving the second request;
returning the reconstructed data to the computer system;
comparing data of the first strip unit with the reconstructed data;
generating reconstructed parity data for the stripe in response to comparing data of the first strip unit with the reconstructed data.
2. The method of claim 1 wherein the reconstructed parity data is generated as a function of all stripe units of the stripe.
3. The method of claim 2 further comprising writing the reconstructed parity data to a parity block of the stripe.
4. In a RAID data storage system, a method comprising:
receiving a first request to read data of a first stripe unit of a stripe, wherein the first request is received from a computer system in data communication with the RAID data storage system;
generating reconstructed data for the first stripe unit in response to receiving the first request;
comparing data of the first stripe unit with the reconstructed data.
5. The method of claim 4 further comprising notifying the computer system of data inconsistency if the comparison shows the data in first stripe unit is different from the reconstructed data.
6. The method of claim 4 wherein the reconstructed data is generated as a function of error correction data and data of stripe units of the stripe other than the first stripe unit.
7. The method of claim 4 further comprising overwriting data for the first stripe unit with the reconstructed data unless the RAID data storage system receives another request to read data of the first stripe unit within a predetermined amount of time.
8. The method of claim 4 further comprising returning the reconstructed data to the computer system.
9. A computer readable medium storing instructions executable by a first computer system in a RAID data storage system, wherein the RAID data storage system comprises a stripe, wherein the stripe comprises a plurality of stripe units including a first stripe unit, wherein the first computer system performs a method in response to executing instructions stored on the computer readable medium, the method comprising:
generating reconstructed data for the first stripe unit in response to the RAID data storage system receiving a first request to read data of a first stripe unit of a stripe, wherein the first request is received from a second computer system in data communication with the RAID data storage system;
comparing data of the first stripe unit with the reconstructed data;
returning the reconstructed data to the computer system.
10. The computer readable medium of claim 9 wherein the method further comprises notifying the computer system of data inconsistency if the comparison shows the data in first stripe unit is different from the reconstructed data.
11. The computer readable medium of claim 9 wherein the reconstructed data is generated as a function of error correction data and data of stripe units of the stripe other than the first stripe unit.
12. The computer readable medium of claim 9 wherein the method further comprises overwriting data for the first stripe unit with the reconstructed data unless the RAID data storage system receives another request to read data of the first stripe unit within a predetermined amount of time.