Patent ID: 7979690

Claim:
A method for booting a computer system from backup, the method comprising: loading an initialization application to run in a single thread mode and that identifies a storage media with the backup that includes boot blocks; installing and activating a handler of a Basic Input/Output System (BIOS) interrupt module, for intercepting boot loader requests to the storage media, and for redirecting them to the backup; creating a bitmap of the data blocks stored in the backup and of a writable data storage device to which new data will be written; initiating the BIOS to load and execute the boot blocks from the backup; transferring control to a routine defined by a boot record stored in the backup's boot blocks; installing and activating an I/O filter for intercepting the requests to the writable data storage device, and after a write request is received, the I/O filter writes a corresponding data block to the writable data storage, and marks this data block in the bitmap to indicate that this block is stored on the writable storage device; after a read request is received, the I/O filter checks the bitmap to see if this data block was not changed, and redirects the read request to the backup to read the data block, and if the requested data block was changed and written to the writeable data storage device, then the I/O filter redirects the read request to the written blocks on the writeable data storage device.