Exploring heterogeneity of unreliable machines for p2p backup

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)

Interest in Solar Photovoltaic (PV) and Peer-To-Peer Energy Trading for Back-Up Electricity in Nigerian Residential Housing Estates

Solar energy presents a highly viable alternative for backup electricity provision in urban Nigeria, as the technology is now mature. Due to widespread electricity black-outs, petrol and diesel generators are widely used, causing local air and noise pollu-tion and contributing to climate change. However, the main clean alternative, solar, has little foothold in the Nigerian energy market. The thesis explores whether households value the “clean power” benefit of the widespread adoption of solar en-ergy for backup electricity in residential estates. It employs a mixed-method ap-proach using semi-structured interviews, a survey, and a discrete choice experiment with 649 respondents in Ibadan, a Nigerian city, to provide insights into preferences for clean and quiet solar PV backup electricity on a residential estate as well as en-ergy trading preferences. Applying quantitative and qualitative methods, the study finds that consumers are interested in dwelling in estates that only permit cleaner backup alternatives, including solar and inverters, compared with the status quo op-tion of staying in estates with petrol or diesel generators. The study also finds that consumers are interested in peer-to-peer energy trading, with differences in prefer-ences for selling and buying excess electricity from neighbours. The thesis also finds that autarky aspirations and financial benefits are key factors that influence partici-pation in energy trading. The findings demonstrate that whilst the electricity supply remains unreliable, there is an opportunity for solar PV to claim a much larger share of the backup electricity market. Furthermore, policymakers and clean energy pro-viders keen to increase the uptake of residential solar energy should highlight the clean and quiet benefits of solar energy for the residents themselves. This research also demonstrates an opportunity to develop and market clean, quiet estates that appeal to people concerned about the health impacts of generator use

An Economist's Guide to Digital Music

In this guide, we discuss the impact of digitalization on the music industry. We rely on market and survey data at the international level as well as expert statements from the industry. The guide investigates recent developments in legal and technological protection of digital music and describes new business models as well as consumers' attitude towards music downloads. We conclude the guide by a discussion of the evolution of the music industry

An Economist's Guide to Digital Music

In this guide, we discuss the impact of digitalization on the music industry. We rely on market and survey data at the international level as well as expert statements from the industry. The guide investigates recent developments in legal and technological protection of digital music and describes new business models as well as consumers' attitude towards music downloads. We conclude the guide by a discussion of the evolution of the music industry.Music; Internet; File-sharing; Peer-to-peer; Piracy; Digital Rights Management; Copyright; E-commerce

Sustainable Availability Provision in Distributed Cloud Services

The article is an extension of this paper 1 . It describes methods for dealing with reliability and fault tolerance issues in cloud-based datacenters. These methods mainly focus on the elimination of a single point of failure within any component of the cloud infrastructure, availability of infrastructure and accessibility of cloud services. Methods for providing the availability of hardware, software and network components are also presented. The analysis of the actual accessibility of cloud services and the mapping of a cloud-based datacenter infrastructure with different levels of reliability to the Tier Classification System2 is described. Non-compliance of the actual accessibility with the level of High Availability for cloud web services is unraveled