Patent ID: 6651137
Filing Date: 2003-11-18
Classification: G06F

Abstract:
A method for controlling a hierarchical RAID system having a plurality of RAIDs in which at lest one RAID composed of a plurality of disks is used as a virtual disk, said method comprising the steps of:a) giving a read-command of existing data and parity from an upper level RAID controlling unit to a lower level RAID controlling unit when a write-command for new data is given from a host computer; b) performing an exclusive OR of the new data, existing data and the parity, and executing a write-transmission in the lower level RAID controlling unit so as to perform a renewal of the parity and the data according to the execution result of the exclusive OR operation; c)generating a command for reading the parity and data of a hard disk in the lower level RAID controlling unit according to the read-command of the step a), and transmitting the command to the upper level RAID controlling unit; and d) evoking a reading for the data and a parity value and performing the exclusive OR so that the write-command given from the upper level RAID controlling unit becomes a write-transmission to each corresponding lower level RAID controlling unit, and executing the write-transmission for the renewal of parity and data.