High performance, enterprise-level data protection system and method provides efficient block-level incremental snapshots of primary storage devices, and instant availability of such snapshots in immediately mountable form that can be directly used in place of the primary storage device. Related systems and applications are described, including an “Enterprise Image Destination” (EID) for backup images; a mirroring technique whereby a replacement physical primary facility may be created while working with a second storage unit as the primary source file system; and a technique for eliminating redundant data in backup images when multiple systems with partially common contents (e.g., operating system files, common databases, application executables, etc.) are being backed up. A number of examples showing “Fast Application Restore” (FAR) with the use of the invention are also provided.