Write cache recovery after loss of power

Details Write cache recovery after loss of power Write cache recovery after loss of power

2006-08-29

2006-08-29

Bonzo, Bryce P. (Department: 2114)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C711S135000

Reexamination Certificate

active

07100080

ABSTRACT:
A method for recovering dirty write cache data after controller power loss or failure from one of two independently battery backed up and mirrored write caches. Two independent controllers jointly operate with a permanent data storage system. Each controller has a write cache that is a mirror of the write cache in the other controller. The primary controller resets a power down flag stored each write cache upon proper shutdown. The primary controller further increments and stores a configuration sequence number into each write cache upon proper shutdown. If a primary controller powers up and identifies that the write cache was not properly shutdown due to the state of the power down flag, it flushes the dirty data in the write cache only if the configuration sequence number contained in the write cache is the same as the configuration sequence number contained in the primary controller. If the configuration sequence number in the primary controller is higher than the configuration sequence number in the write cache, the dirty data was previously flushed to permanent data storage with the other write cache.

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