Enhanced raid write hole protection and recovery
US5774643A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 13, 1995 |
| Grant date | Jun 30, 1998 |
| Priority date | — |
| Expiry date | Oct 13, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2211/1009
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Disclosed is a method and apparatus for reconstructing data in a computer system employing a modified RAID 5 data protection scheme. The computer system includes a write back cache composed of non-volatile memory for storing (1) writes outstanding to a device and associated data read, and (2) storing metadata information in the non-volatile memory. The metadata includes a first field containing the logical block number or address (LBN or LBA) of the data, a second field containing the device ID, and a third field containing the block status. From the metadata information it is determined where the write was intended when the crash occurred. An examination is made to determine whether parity is consistent across the slice, and if not, the data in the non-volatile write back cache is used to reconstruct the write that was occurring when the crash occurred to insure consistent parity, so that only those blocks affected by the crash have to be reconstructed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.