Evangelos Kotsovinos

Bio: Evangelos Kotsovinos is an academic researcher from Deutsche Telekom. The author has contributed to research in topics: Virtual machine & Trust management (information system). The author has an hindex of 15, co-authored 29 publications receiving 1298 citations. Previous affiliations of Evangelos Kotsovinos include University of Cambridge & Technical University of Berlin.

Live wide-area migration of virtual machines including local persistent state

Abstract: So far virtual machine (VM) migration has focused on transferring the run-time memory state of the VMs in local area networks (LAN). However, for wide-area network (WAN) migration it is crucial to not just transfer the VMs image but also transfer its local persistent state (its file system) and its on-going network connections. In this paper we address both: by combining a block-level solution with pre-copying and write throttling we show that we can transfer an entire running web server, including its local persistent state, with minimal disruption --- three seconds in the LAN and 68 seconds in the WAN); by combining dynDNS with tunneling, existing connections can continue transparently while new ones are redirected to the new network location. Thus we show experimentally that by combining well-known techniques in a novel manner we can provide system support for migrating virtual execution environments in the wide area.

Method and system for the transparent migration of virtual machines storage

Abstract: Method for transferring storage data of a virtual machine to be migrated from a first host device to a second host device via a communication network, including: running the virtual machine on the first host device; storing, on a local storage device of the first host device, a disk image used by the virtual machine; detecting, while the virtual machine is running on the first host device, any changes made to the disk image used by the virtual machine; establishing a connection over the communication network from the first host device to the second host device; transferring, to the second host device while the virtual machine is running on the first host device, the disk image used by the virtual machine and the detected any changes made; modifying the disk image transferred to the second host device in response to the detected any changes transferred to the second host device; and starting, using the modified disk image, a migrated virtual machine on the second host device at a current state of the virtual machine running on the first host device.

Are virtual machine monitors microkernels done right

Abstract: Rob Pike has irreverently suggested that “systems software research is irrelevant”, implying that academic systems research has negligible impact outside the university. In Section 4, we claim that VMMs provide a platform on which innovative systems research ideas can be developed and deployed. We believe that providing a common framework for hosting novel systems will increase the penetration and relevance of systems research.

Method and system for automatic and remote server provisioning using virtual machine appliances

Abstract: The proposed system allows the automatic remote provisioning of servers. Using a system, when a new out-of-the-box server is connected to a network, an operating system and applications are supposed to be automatically deployed on it, without further manual action. To achieve this, the system supports storing server provisioning and configuration information in a central database, and associating this information with specific physical serves; automatically retrieving the suitable provisioning and configuration information for a server when it connects to the network; and automatically deploying and starting the applications defined in the provisioning and configuration information on the server.

Pinocchio: Incentives for Honest Participation in Distributed Trust Management

Abstract: In this paper, we introduce a framework for providing incentives for honest participation in global-scale distributed trust management infrastructures. Our system can improve the quality of information supplied by these systems by reducing free-riding and encouraging honesty. Our approach is twofold: (1) we provide rewards for participants that advertise their experiences to others, and (2) impose the credible threat of halting the rewards, for a substantial amount of time, for participants who consistently provide suspicious feedback. For this purpose we develop an honesty metric which can indicate the accuracy of feedback.

Xen and the art of virtualization

Abstract: Numerous systems have been designed which use virtualization to subdivide the ample resources of a modern computer. Some require specialized hardware, or cannot support commodity operating systems. Some target 100% binary compatibility at the expense of performance. Others sacrifice security or functionality for speed. Few offer resource isolation or performance guarantees; most provide only best-effort provisioning, risking denial of service.This paper presents Xen, an x86 virtual machine monitor which allows multiple commodity operating systems to share conventional hardware in a safe and resource managed fashion, but without sacrificing either performance or functionality. This is achieved by providing an idealized virtual machine abstraction to which operating systems such as Linux, BSD and Windows XP, can be ported with minimal effort.Our design is targeted at hosting up to 100 virtual machine instances simultaneously on a modern server. The virtualization approach taken by Xen is extremely efficient: we allow operating systems such as Linux and Windows XP to be hosted simultaneously for a negligible performance overhead --- at most a few percent compared with the unvirtualized case. We considerably outperform competing commercial and freely available solutions in a range of microbenchmarks and system-wide tests.

Designing an Super-Peer Network

Abstract: A super-peer is a node in a peer-to-peer network that operates both as a server to a set of clients, and as an equal in a network of super-peers. Super-peer networks strike a balance between the efficiency of centralized search, and the autonomy, load balancing and robustness to attacks provided by distributed search. Furthermore, they take advantage of the heterogeneity of capabilities (e.g., bandwidth, processing power) across peers, which recent studies have shown to be enormous. Hence, new and old P2P systems like KaZaA and Gnutella are adopting super-peers in their design. Despite their growing popularity, the behavior of super-peer networks is not well understood. For example, what are the potential drawbacks of super-peer networks? How can super-peers be made more reliable? How many clients should a super-peer take on to maximize efficiency? we examine super-peer networks in detail, gaming an understanding of their fundamental characteristics and performance tradeoffs. We also present practical guidelines and a general procedure for the design of an efficient super-peer network.

Remus: high availability via asynchronous virtual machine replication

Abstract: Allowing applications to survive hardware failure is an expensive undertaking, which generally involves reengineering software to include complicated recovery logic as well as deploying special-purpose hardware; this represents a severe barrier to improving the dependability of large or legacy applications. We describe the construction of a general and transparent high availability service that allows existing, unmodified software to be protected from the failure of the physical machine on which it runs. Remus provides an extremely high degree of fault tolerance, to the point that a running system can transparently continue execution on an alternate physical host in the face of failure with only seconds of downtime, while completely preserving host state such as active network connections. Our approach encapsulates protected software in a virtual machine, asynchronously propagates changed state to a backup host at frequencies as high as forty times a second, and uses speculative execution to concurrently run the active VM slightly ahead of the replicated system state.

Context-aware systems

Abstract: Nowadays, numerous journals and conferences have published articles related to context-aware systems, indicating many researchers' interest. Therefore, the goal of this paper is to review the works that were published in journals, suggest a new classification framework of context-aware systems, and explore each feature of classification framework. This paper is based on a literature review of context-aware systems from 2000 to 2007 using a keyword index and article title search. The classification framework is developed based on the architecture of context-aware systems, which consists of the following five layers: concept and research layer, network layer, middleware layer, application layer and user infrastructure layer. The articles are categorized based on the classification framework. This paper allows researchers to extract several lessons learned that are important for the implementation of context-aware systems.

A Robust Reputation System for P2P and Mobile Ad-hoc Networks

Abstract: Reputation systems can be tricked by the spread of false reputation ratings, be it false accusations or false praise. Simple solutions such as exclusively relying on one’s own direct observations have drawbacks, as they do not make use of all the information available. We propose a fully distributed reputation system that can cope with false disseminated information. In our approach, everyone maintains a reputation rating and a trust rating about everyone else that they care about. From time to time first-hand reputation information is exchanged with others; using a modified Bayesian approach we designed and present in this paper, only second-hand reputation information that is not incompatible with the current reputation rating is accepted. Thus, reputation ratings are slightly modified by accepted information. Trust ratings are updated based on the compatibility of second-hand reputation information with prior reputation ratings. Data is entirely distributed: someone’s reputation and trust is the collection of ratings maintained by others. We enable redemption and prevent the sudden exploitation of good reputation built over time by introducing re-evaluation and reputation fading.