Alexander Papaspyrou

Toward an Open Cloud Standard

Todays cloud ecosystem features several increasingly divergent management interfaces. Numerous bridging efforts attempt to ameliorate the resulting vendor lock-in for customers. However, as the number of providers continues to grow, the drawback of this approach becomes apparent: the need to maintain adapter implementations. The Open Cloud Computing Interface builds on the fundamentals of modern Web-based services to define a standardized interface for cloud environments while enabling service providers to differentiate their service offerings at the same time.

On grid performance evaluation using synthetic workloads

Grid computing is becoming a common platform for solving large scale computing tasks. However, a number of major technical issues, including the lack of adequate performance evaluation approaches, hinder the grid computings further development. The requirements herefore are manifold; adequate approaches must combine appropriate performance metrics, realistic workload models, and flexible tools for workload generation, submission, and analysis. In this paper we present an approach to tackle this complex problem. First, we introduce a set of grid performance objectives based on traditional and grid-specific performance metrics. Second, we synthesize the requirements for realistic grid workload modeling, e.g. co-allocation, data and network management, and failure modeling. Third, we show how GRENCHMARK, an existing framework for generating, running, and analyzing grid workloads, can be extended to implement the proposed modeling techniques. Our approach aims to be an initial and necessary step towards a common performance evaluation framework for grid environments.

Prospects of collaboration between compute providers by means of job interchange

This paper empirically explores the advantages of the collaboration between different parallel compute sites in a decentralized grid scenario. To this end, we assume independent users that submit their jobs to their local site installation. The sites are allowed to decline the local execution of jobs by offering them to a central job pool. In our analysis we evaluate the performance of three job sharing algorithms that are based on the commonly used algorithms First-Come-First-Serve, EASY Backfilling, and List-Scheduling. The simulation results are obtained using real workload traces and compared to single site results. We show that simple job pooling is beneficial for all sites even if the local scheduling systems remain unchanged. Further, we show that it is possible to achieve shorter response times for jobs compared to the best single-site scheduling results.

Open Cloud Computing Interface in Data Management-Related Setups

The Cloud community is a vivid group of people who drive the ideas of Cloud computing into different fields of Information Technology. This demands for standards to ensure interoperability and avoid vendor lock-in. Since such standards need to satisfy many requirements, use cases, and applications, they need to be extremely flexible and adaptive. The Open Cloud Computing Interface (OCCI) family of specifications aims to achieve this goal: originally developed for the deployment of infrastructure Clouds, it can also be used in different service and deployment models. This article will outline the OCCI specifications and demonstrate how they can be used in data management-related setups. Not only can OCCI be easily integrated but it can also be used to deploy data-centric applications (which are secured by SLAs), support data-awareness in scheduling, as well as directly interface with data management tools in a PaaS-based manner. To demonstrate this, three use cases are discussed in this article.

A proposal for WS-Agreement Negotiation

The Web Services Agreement specification defines a normative language to formulate Service Level Agreements and a basic protocol to expose service-level descriptions, validate service-level requests, and come to an agreement. This protocol, often called “take-it-or-leave-it”, allows a service provider and a service consumer to decide whether to accept or reject a service offer. Although this approach is sufficient for a number of use cases, others exist with requirements for multi-step negotiation or the adaptation of an existing agreement. In this paper, we describe the Web Services Agreement Negotiation protocol, a proposal by the Open Grid Forum to extend the existing specification. This proposal is the result of combining various research activities that have been conducted to define protocols for negotiating service levels or to supersede the existing “take-it-or-leave-it” protocol. The main characteristics of this proposal are the multi-round negotiation capability, renegotiation capability, and compliance with the original specification.

Robust Load Delegation in Service Grid Environments

In this paper, we address the problem of finding well-performing workload exchange policies for decentralized Computational Grids using an Evolutionary Fuzzy System. To this end, we establish a noninvasive collaboration model on the Grid layer which requires minimal information about the participating High Performance and High Throughput Computing (HPC/HTC) centers and which leaves the local resource managers completely untouched. In this environment of fully autonomous sites, independent users are assumed to submit their jobs to the Grid middleware layer of their local site, which in turn decides on the delegation and execution either on the local system or on remote sites in a situation-dependent, adaptive way. We find for different scenarios that the exchange policies show good performance characteristics not only with respect to traditional metrics such as average weighted response time and utilization, but also in terms of robustness and stability in changing environments.

Decentralized Grid Scheduling with Evolutionary Fuzzy Systems

In this paper, we address the problem of finding workload exchange policies for decentralized Computational Grids using an Evolutionary Fuzzy System. To this end, we establish a non-invasive collaboration model on the Grid layer which requires minimal information about the participating High Performance and High Throughput Computing (HPC/HTC) centers and which leaves the local resource managers completely untouched. In this environment of fully autonomous sites, independent users are assumed to submit their jobs to the Grid middleware layer of their local site, which in turn decides on the delegation and execution either on the local system or on remote sites in a situation-dependent, adaptive way. We find for different scenarios that the exchange policies show good performance characteristics not only with respect to traditional metrics such as average weighted response time and utilization, but also in terms of robustness and stability in changing environments.

Exploring the behavior of building blocks for multi-objective variation operator design using predator-prey dynamics

In this paper, we utilize a predator-prey model in order to identify characteristics of single-objective variation operators in the multi-objective problem domain. In detail, we analyze exemplarily Gaussian mutation and simplex recombination to find explanations for the observed behaviorswithin this model. Then, both operators are combinedto a new complex one for the multi-objective case in order to aggregate the identified properties. Finally, we show that (a) characteristic properties can still be observed in the combination and (b) the collaboration of those operators is beneficial for solving an exemplary multi-objective problem regarding convergence and diversity.

Discovering performance bounds for grid scheduling by using evolutionary multiobjective optimization

In this paper, we introduce a methodology for the approximation of optimal solutions for a resource allocation problem in the domain of Grid scheduling on High Performance Computing systems. In detail, we review a real-world scenario with decentralized, equitable, and autonomously acting suppliers of compute power who wish to collaborate in the provision of their resources. We exemplarily apply NSGA-II in order to explore the bounds of maximum achievable benefit. To this end, appropriate encoding schemes and variation operators are developed while the performance is evaluated. The simulations are based upon recordings from real-world Massively Parallel Processing systems that span a period of eleven months and comprise approximately 100,000 jobs. By means of the obtained Pareto front we are able to identify bounds for the maximum benefit of Grid computing in a popular scenario. For the first time, this enables Grid scheduling researchers to rank their developed real-world strategies.

Towards A Standards-Based Grid Scheduling Architecture

The definition of a generic Grid scheduling architecture is t he concern of both the Open Grid Forum’s Grid Scheduling Architecture Research Group and a CoreGRID research group of the same name. Such an architecture should provide a blueprint for Grid system and middleware designers and assist them in linking their scheduling requirements to diverse existing solutions and standards. Based on work executed within OGF related to scheduling use cases and requirements, which tackles the problem from a more theoretical point of view, we approach in this paper the problem practically by evaluating the teikoku scheduling framework in the light of standards-compliance. The results of this evaluation and the existing Grid Scheduling Architecture proposal are set into context, existing ga ps are described and potential solutions to bridge them are int roduced. In doing so, we concentrate on the interoperability of schedulers and the necessity of a Scheduling Description Language to achieve it.