Download Time Analysis for Distributed Storage Codes with Locality and Availability

Mehmet Fatih Aktas, Swanand Kadhe, Emina Soljanin, Alex Sprintson

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The paper presents techniques for analyzing the expected download time in distributed storage systems that employ systematic availability codes. These codes provide access to hot data through the systematic server containing the object and multiple recovery groups. When a request for an object is received, it can be replicated (forked) to the systematic server and all recovery groups. We first consider the low-traffic regime and present the close-form expression for the download time. By comparison across systems with availability, maximum distance separable (MDS), and replication codes, we demonstrate that availability codes can reduce download time in some settings but are not always optimal. In the high-traffic regime, the system contains multiple inter-dependent Fork-Join queues, making exact analysis intractable. Accordingly, we present upper and lower bounds on the download time, and an M/G/1 queue approximation for several cases of interest. Via extensive numerical simulations, we evaluate our bounds and demonstrate that the M/G/1 queue approximation has a high degree of accuracy.

Original languageEnglish (US)
Article number9381261
Pages (from-to)3898-3910
Number of pages13
JournalIEEE Transactions on Communications
Volume69
Issue number6
DOIs
StatePublished - Jun 2021

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering

Keywords

  • Distributed coded storage
  • availability
  • download with redundancy

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