Eliana-Dina Tirsa

A dependability layer for large-scale distributed systems

Ensuring dependability in large-scale distributed systems represents an important research subject today. Despite the fact that many projects obtained valuable results in this domain, no acceptable solution was yet found that could integrate all the requirements for designing a dependable system and that could exploit all the capabilities of modern systems. We present a unitary and aggregate approach to ensuring reliability, availability, safety and security of distributed systems. Starting from the proposed architecture, we present implementation details for two solutions designed to ensure fault tolerance, using virtualisation and container-based replication of services. We also present an approach to enhance security using combined modern security models in large-scale distributed systems. The results and implementation details can serve as a methodology to assist distributed infrastructures in adopting such a middleware layer designed to enforce dependability in large-scale distributed systems.

A fault-tolerant peer-to-peer object storage architecture with multidimensional range search capabilities and adaptive topology

In this paper we present a fault-tolerant, collaborative peer-to-peer object storage architecture with adaptive topology and efficient multidimensional range search capabilities. Every stored object has a fixed set of index properties, whose ranges of values form a multidimensional geometric property space. The architecture efficiently supports multidimensional range queries by mapping the peer identifiers into the property space of the stored objects. The potential disadvantage of not balancing the load on the peers which may be caused by this approach in the case of a static topology is addressed by introducing a dynamic topology, which attempts to balance the storage load. The architecture seamlessly supports dynamic node arrivals and departures.

A peer-to-peer architecture for multi-path data transfer optimization using local decisions

Data management (data retrieval and processing) performance in large-scale distributed systems (e.g. Grids, distributed databases, content delivery networks) is directly dependent on the efficiency and reliability of the communication architecture. The communication layer is responsible for transferring data between multiple source-destination pairs or for gathering the data from multiple sources to the processing nodes. In this paper we propose a peer-to-peer communication architecture for optimizing the efficiency, load balancing and reliability of the data transfers in the system, making local decisions only. We also present simulation-based experimental evaluation results.

Towards a Real-Time Scheduling Framework for Data Transfers in Tree Networks

As the amount of transferred data increases world-wide, network data transfers may exhibit poor performance due to resource usage conflicts, even when enough resources are available (at a different place or at another time). Thus, efficient resource management and intelligent scheduling of the data transfers are required. These problems are, however, quite difficult to solve, both from a theoretical and a practical perspective. In this paper we propose several novel algorithmic techniques for the real-time scheduling of data transfers when the network has a tree topology. Some of these techniques can be later implemented in a (re)configurable data transfer scheduling framework.

An Application-Assisted Checkpoint-Restart Mechanism for Java Applications

In this paper we present a novel application-assisted checkpoint-restart mechanism for Java applications. The checkpoint-restart API provides the application developers with full control over what data needs to be check-pointed. The novelty of our system is that it allows different checkpoint periods for different data items. Our implementation makes full use of the Java Reflection API.

Towards Configurable Building Blocks for the Development of Distributed Services: Resource Selection and Communication Protocols

In this paper we argue our view for providing a set of configurable building blocks for the development of distributed services and discuss in detail the architecture of two such blocks: a fault-tolerant, fully decentralized resource selection component to be used in virtual Cloud-like environments (not necessarily restricted to clusters) and a Python-based framework for developing point-to-point communication protocols. The resource selection component is based on a multidimensional P2P object storage architecture where a set of peers manage a large number of objects.

Data replication techniques with applications to the MonALISA distributed monitoring system

In this paper we tackle several problems regarding efficient data replication in distributed systems. In the first part, we consider several theoretical offline data replication and reliability improvement problems, for which we present novel, efficient, algorithmic solutions (e.g. replication in tree networks and reliable replication strategies). In the second part we address a concrete data replication and load balancing problem, motivated by the MonALISA distributed monitoring system, for which we present a replication scheme based on the presence of a load balancer.

Scalable Chord-Based, Cluster-Enhanced Peer-to-Peer Architecture Supporting Range Queries

Over the Internet today, computing and communications environments are more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. Peer-to-Peer network overlays provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. We present a scalable, cluster-enhanced P2P overlay network designed to share large sets of replicated distributed objects in the context of large-scale highly dynamic infrastructures. The system extends an existing architecture with an original solution designed to achieve optimal implementation results for range queries, as well as provide a fault-tolerant substrate. It also optimizes message routing in hop-count and throughput, whilst providing an adequate consistency among replicas.