Patent ID: 6173361
Filing Date: 2001-01-09
Classification: G06F

Abstract:
A disk control device operationally connected to a high-order device for operating a plurality of disk devices, and having a cache for storing a plurality of data blocks including a plurality of parity data from a corresponding plurality of parity groups in the plurality of disk devices, said disk control device comprising:a cache management table for indicating positions of the data blocks stored in the cache;cache management means for transferring a selected data block requested by the high-order device from the plurality of disk devices to the cache when said cache management table indicates that said selected data block is not stored in the cache; andcontrol means for transferring said selected data block from said cache to said high-order device when said cache management means informs said control means that said selected data block is stored in the cache;wherein said cache management means holds a selected parity data in the cache when at least one data block belonging to the same one of the plurality of parity groups as said selected parity data is stored in the cache, and expels said selected parity data from the cache when none of the data blocks belonging to the same one of the plurality of parity groups as said selected parity data are stored in the cache.