Patent ID: 8843602

Claim:
A network boot system wherein a network boot server which provides a disk image including an operating system operating on a client terminal as a virtual disk and a client terminal including a physical storage device are connected to each other over a network, the client terminal includes a physical memory which can temporarily store data necessary during boot-up of the operating system and a network interface for accessing the server over the network, the operating system includes a filter driver for converting access to a local bus of the client terminal into access to the network, and a read cache driver for driving the storage device, and the read cache driver includes a read cache mechanism that read-caches data read out from the network boot server by the filter driver on the storage device; wherein the read cache mechanism includes a read cache area for holding data received from the server and a cache management area for writing back at least a part of a management flag for determining by the read cache driver whether the data read out from the server is in an already-written state that is held in the physical memory; wherein the read cache driver in configured to receive a write request signal to the read cache area, whereby the physical memory is configured in response to store an indicator that the write request signal has been received, and whereby the read cache driver is configured to not use the read cached data of the read cache area; the network boot system comprising, a micro-processor, a first computer storage location that stores a revision of data of the virtual disk, a second computer storage location that stores a revision of the read cached data of the read cache area, where-in the micro-processor compares the first and second revisions at a time of a client terminal boot-up or at a time when the client terminal side mounts the boot image as a virtual disk over the network, and the micro-processor determines an operation of the read cache driver based on the comparison result.