1. Download Time Analysis for Distributed Storage Codes With Locality and Availability
- Author
-
Emina Soljanin, Alex Sprintson, Mehmet Aktaş, and Swanand Kadhe
- Subjects
FOS: Computer and information sciences ,Computer Science - Performance ,Download ,Computer science ,Computer Science - Information Theory ,Information Theory (cs.IT) ,Distributed computing ,Locality ,020206 networking & telecommunications ,02 engineering and technology ,Upper and lower bounds ,Replication (computing) ,Performance (cs.PF) ,Redundancy (information theory) ,Computer Science - Distributed, Parallel, and Cluster Computing ,020204 information systems ,Server ,Distributed data store ,0202 electrical engineering, electronic engineering, information engineering ,Distributed, Parallel, and Cluster Computing (cs.DC) ,Electrical and Electronic Engineering ,Queue - 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 consists of 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., Comment: Accepted for a publication in IEEE Transactions on Communications
- Published
- 2021