PARITY UPDATE FOOTPRINTS KEPT ON DISK

摘要

Parity Update Footprints (PUFPs) are kept on the disk drives themselves (rather than in nonvolatile RAM) so that the PUFPs will move along with the RAID arrays and data they protect. This permits effective detection of and recovery from many unexpected-power-loss events, and certain other types of failures, even in a clustered-adapter configuration or with a standalone adapter that has no nonvolatile RAM or only a little nonvolatile RAM. Desirably, many Set PUFP and Clear PUFP operations can be coalesced into each write to the block on the disk which contains the PUFPs, thereby improving system performance.