Patent ID: 6182198
Filing Date: 2001-01-30
Classification: G06F,Y10S

Abstract:
A method of performing a snapshot backup of a storage unit of a host system including at least one primary system drive, at least one log system drive and at least one backup logic unit while allowing normal read operations and write operations to occur, comprising:a) processing a write operation of new data submitted to a primary logic unit to be written to at least one sector of the primary system drive during the snapshot backup including:i) reading old data on the primary system drive that is to be overwritten by the new data in response to the write operation;ii) buffering the old data;iii) overwriting the old data with the new data; andiv) writing the old data to the log system drive if the write operation is a first write operation to the sector in the primary system drive for the snapshot backup:(b) processing a read operation submitted to the backup logic unit during the snapshot backup including:i) accessing requested data of the read operation from the log system drive if the requested data is available from the log system drive and returning the requested data:ii) accessing the requested data from the primary system drive if the requested data is not available from the log system drive and returning the requested data.