Can We Really Recover Data if Storage Subsystem Fails?

This paper presents a theoretical and experimental study on the limitations of copy-on-write snapshots and incremental backups in terms of data recoverability. We provide mathematical proofs of our new findings as well as implementation experiments to show how data recovery is done in case of various failures. Based on our study, we propose a new system architecture that will overcome the problems of existing technologies. The new architecture can provide two-way data recovery capability with the same storage overheads and can be implemented fairly easily on existing systems. We show that the new architecture has maximum data recoverability and is practically feasible.