Mean-Field Analysis of Coding Versus Replication in Large Data Storage Systems
Abstract
We study cloud storage systems with a very large number of files stored in a very large number of servers. In such systems, files are either replicated or coded to ensure reliability, i.e., to guarantee file recovery from server failures. This redundancy in storage can further be exploited to improve system performance (mean file-access delay) through appropriate load-balancing (routing) schemes. However, it is unclear whether coding or replication is better from a system performance perspective since the corresponding queueing analysis of such systems is, in general, quite difficult except for the trivial case when the system load asymptotically tends to zero. Here, we study the more difficult case where the system load is not asymptotically zero. Using the fact that the system size is large, we obtain a mean-field limit for the steady-state distribution of the number of file access requests waiting at each server. We then use the mean-field limit to show that, for a given storage capacity per file, coding strictly outperforms replication at all traffic loads while improving reliability. Further, the factor by which the performance improves in the heavy traffic is at least as large as in the light-traffic case. Finally, we validate these results through extensive simulations.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 13, 2018
- Source ID
- 10.1145/3159172
Entities
People
- Aditya Ramamoorthy
- Bin Li
- R. Srikant
Organizations
- Defense Threat Reduction Agency
- Iowa State University
- National Science Foundation
- University of Illinois Urbana–Champaign
- University of Rhode Island