Estimating unseen deduplication - From theory to practice

Abstract

Estimating the deduplication ratio of a very large dataset is both extremely useful, but genuinely very hard to perform. In this work we present a new method for accurately estimating deduplication benefits that runs 3X to 15X faster than the state of the art to date. The level of improvement depends on the data itself and on the storage media that it resides on. The technique is based on breakthrough theoretical work by Valiant and Valiant from 2011, that give a provably accurate method for estimating various measures while seeing only a fraction of the data. However, for the use case of deduplication estimation, putting this theory into practice runs into significant obstacles. In this work, we find solutions and novel techniques to enable the use of this new and exciting approach. Our contributions include a novel approach for gauging the estimation accuracy, techniques to run it with low memory consumption, a method to evaluate the combined compression and deduplication ratio, and ways to perform the actual sampling in real storage systems in order to actually reap benefits from these algorithms. We evaluated our work on a number of real world datasets.