Patent ID: 6591336
Filing Date: 2003-07-08
Classification: G06F

Abstract:
An external-storage sharing system including a plurality of host devices and an external storage device which is connected to each of the plurality of host devices, and each of said plurality of host devices having a cache retaining a portion of data stored in said external storage device, and wherein:each of said plurality of host devices includes: write-informing means for informing any other one of said plurality of host devices and said external storage device that the data is to be written and for sending information representing a block including the data to be written in a case where data is to be written in its own cache, data-requesting means for requesting said external storage device to transmit the data of the block in a case where data of the block sent from said write-informing means of any one of said plurality of host devices is to be written or read, and data-reading/writing means for reading or writing the data after the data of the block is written back into said external storage device in response to the requesting of said data-requesting means; and said external storage device includes data-write-back means for writing back the data of the block from the cache of one of said plurality of host devices including said write-informing means having informed that the data has been written, in a case where transmission of data is requested from said data-requesting means of any one of said plurality of host devices, and data transmission means for transmitting the data of the block to the cache of one of said plurality of host devices including said data-requesting means having requested the transmission of the data, after the data of the block is written back into said external storage device by said data-write-back means.