Exploring heterogeneity of unreliable machines for p2p backup

TL;DR

This paper presents a p2p backup system architecture that leverages machine heterogeneity and dynamic contracts to optimize data replication, demonstrating effectiveness despite high machine unreliability.

Contribution

It introduces a novel p2p backup architecture using pairwise contracts for optimized replica placement considering machine heterogeneity and availability.

Findings

System remains effective with only 13% machine availability.

Availability of machines is the main factor affecting system quality.

Efficient backup is possible on highly unreliable machines.

Abstract

P2P architecture is a viable option for enterprise backup. In contrast to dedicated backup servers, nowadays a standard solution, making backups directly on organization's workstations should be cheaper (as existing hardware is used), more efficient (as there is no single bottleneck server) and more reliable (as the machines are geographically dispersed). We present the architecture of a p2p backup system that uses pairwise replication contracts between a data owner and a replicator. In contrast to standard p2p storage systems using directly a DHT, the contracts allow our system to optimize replicas' placement depending on a specific optimization strategy, and so to take advantage of the heterogeneity of the machines and the network. Such optimization is particularly appealing in the context of backup: replicas can be geographically dispersed, the load sent over the network can be minimized, or the optimization goal can be to minimize the backup/restore time. However, managing the contracts, keeping them consistent and adjusting them in response to dynamically changing environment is challenging. We built a scientific prototype and ran the experiments on 150 workstations in the university's computer laboratories and, separately, on 50 PlanetLab nodes. We found out that the main factor affecting the quality of the system is the availability of the machines. Yet, our main conclusion is that it is possible to build an efficient and reliable backup system on highly unreliable machines (our computers had just 13% average availability).