Heuristics for Analyzing Download Time in MDS Coded Storage Systems

There has been a growing interest, in both theory and practice, in using the available redundancy in storage systems for mitigating stragglers in content download. This paper is concerned with MDS coded storage systems and studies (n, k) data access model. When $k$ = n, system is equivalent to a fork-join queue, which is known to be notoriously hard to analyze, while system with $k$ = 1 has been previously shown to be equivalent to an M/G/1 queue. We here argue that the system with $k$ = 2 is of practical interest, and then present a method that approximates the system as an M/G/1 queue. Approximated download time is shown to be more accurate than the bounds available in the literature. We also note that the presented method can be used for approximating systems that employ other newly designed and deployed storage codes.