Life or death at block-level

A fundamental piece of information required in intelligent storage systems is the liveness of data. We formalize the notion of liveness within storage, and present two classes of techniques for making storage systems liveness-aware. In the explicit notification approach, we present robust techniques by which a file system can impart liveness information to storage through a "free block" command. In the implicit detection approach, we show that such information can be inferred by the storage system efficiently underneath a range of file systems, without changes to the storage interface. We demonstrate our techniques through a prototype implementation of a secure deleting disk. We find that while the explicit interface approach is desirable due to its simplicity, the implicit approach is easy to deploy and enables quick demonstration of new functionality, thus facilitating rapid migration to an explicit interface.