Section: New Results

Flash-Based Data Management

Participants : Nicolas Anciaux, Matias Bjørling, Philippe Bonnet, Luc Bouganim [correspondent] , Niv Dayan, Philippe Pucheral.

Mass-storage secure portable tokens are emerging and provide a real breakthrough in the management of sensitive data. They can embed personal data and/or metadata referencing documents stored encrypted in the Cloud and can manage them under holder's control. Mass on-board storage requires efficient embedded database techniques. These techniques are however very challenging to design due to a combination of conflicting NAND Flash constraints and scarce RAM constraint, disqualifying known state of the art solutions. To tackle this challenge, we proposed a log-only based storage organization and an appropriate indexing scheme, which (1) produce only sequential writes compatible with the Flash constraints and (2) consume a tiny amount of RAM, independent of the database size [13] .

Solid State Drives (SSDs) are a moving target for system designers: they are black boxes, their internals are undocumented, and their performance characteristics vary across models. There is no appropriate analytical model and experimenting with commercial SSDs is cumbersome, as it requires a careful experimental methodology to ensure repeatability. Worse, performance results obtained on a given SSD cannot be generalized. Overall, it is impossible to explore how a given algorithm, say a hash join or LSM-tree insertions, leverages the intrinsic parallelism of a modern SSD, or how a slight change in the internals of an SSD would impact its overall performance. In 2013, we worked on a new SSD simulation framework, named EagleTree, which addresses these problems, and enables a principled study of SSD-Based algorithms. We published a demonstration on EagleTree at VLDB'13 [20] . The demonstration scenario illustrates the design space for algorithms based on an SSD-based IO stack, and shows how researchers and practitioners can use EagleTree to perform tractable explorations of this complex design space.