Repair Time in Distributed Storage Systems

Abstract

AbstractIn this paper, we analyze a highly distributed backup storage system realized by means of nano datacenters (NaDa). NaDa have been recently proposed as a way to mitigate the growing energy, bandwidth and device costs of traditional data centers, following the popularity of cloud computing. These service provider-controlled peer-to-peer systems take advantage of resources already committed to always-on set top boxes, the fact they do not generate heat dissipation costs and their proximity to users.In this kind of systems redundancy is introduced to preserve the data in case of peer failures or departures. To ensure long-term fault tolerance, the storage system must have a self-repair service that continuously reconstructs the fragments of redundancy that are lost. In the literature, the reconstruction times are modeled as independent. In practice, however, numerous reconstructions start at the same time (when the system detects that a peer has failed).We propose a new analytical framework that takes into account this correlation when estimating the repair time and the probability of data loss. We show that the load is unbalanced among peers (young peers inherently store less data than the old ones). The models and schemes proposed are validated by mathematical analysis, extensive set of simulations, and experimentation using the GRID5000 test-bed platform. This new model allows system designers to operate a more accurate choice of system parameters in function of their targeted data durability.KeywordsStorage SystemMarkov Chain ModelDistribute Hash TableRepair TimeReconstruction TimeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.