On the Stability of Redundancy Models

Abstract

The main motivation to investigate redundancy models comes from empirical evidence suggesting that redundancy can help improve the performance of real-world applications. Although there are several variants of a redundancy-based system, the general notion of redundancy is to create multiple copies of the same job that will be sent to a subset of servers. By allowing for redundant copies, the aim is to minimize the system latency by exploiting the variability in the queue lengths and the capacity of the different servers. In this article, the stability condition of redundancy multiserver systems is investigated. Several popular scheduling disciplines are considered, such as first-come-first-serve (FCFS), processor sharing (PS), and random order of service (ROS) and show that whereas with ROS the performance is not reduced, with both PS and FCFS the performance can severely degrade.