Rafael Bohrer Ávila

The MultiCluster Model to the Integrated Use of Multiple Workstation Clusters

One of the new research tendencies within the well-established cluster computing area is the growing interest in the use of multiple workstation clusters as a single virtual parallel machine, in much the same way as individual workstations are nowadays connected to build a single parallel cluster. In this paper we present an analysis on several aspects concerning the integration of different workstation clusters, such as Myrinet and SCI, and propose our MultiCluster model as an alternative to achieve such integrated architecture.

Performance evaluation of a prototype distributed NFS server

A high-performance file system is normally a key point for large cluster installations, where hundreds or even thousands of nodes frequently need to manage large volumes of data. While most solutions usually make use of dedicated hardware and/or specific distribution and replication protocols, the NFSP (NFS Parallel) project aims at improving performance within a standard NFS client/server system. In this paper we investigate the possibilities of a replication model for the NFS server, which is based on Lasy Release Consistency (LRC). A prototype has been built upon the user-level NFSv2 server and a performance evaluation is carried out.

Processing Mesoscale Climatology in a Grid Environment

Enhancing the quality of weather and climate forecasts are central scientific research objectives worldwide. However, simulations of the atmosphere, usually demand high processing power and large storage resources. In this context, we present the GBRAMS project, that applies grid computing to speed up the generation of a regional model climatology for Brazil. A grid infrastructure was built to perform long-term integrations of a mesoscale numerical model (BRAMS), managing a queue of up to nine independent jobs submitted to three clusters spread over Brazil- Three distinct middlewares, Globus Toolkit, OurGrid and OAR/CIGRI, were compared in their ability to manage these jobs, and results on the usage of each node of the grid are provided. We analyze the impact of the resulted climatology in the accuracy of climate forecast, showing model bias removal which indicates correctness of the generated climatology. Our central contribution are how to use grid computing to speed-up climatology generation and the middleware impact on this enterprise.

Performance analysis of DECK collective communication service

Collective communication is very useful for parallel applications, especially those in which matrix and vector data structures need to be manipulated by a group of processes. We present a performance analysis of collective communication primitives designed for the DECK parallel programming environment, with the aid of different numerical methods used to solve hydrodynamics and mass transportation models.

Combining Multiple Metrics to Control BSP Process Rescheduling in Response to Resource and Application Dynamics

This article discusses MigBSP: a rescheduling model that acts on Bulk Synchronous Parallel applications running over computational Grids. It combines the metrics Computation, Communication and Memory to make migration decisions. MigBSP also offers efficient adaptations to reduce its overhead. Additionally, MigBSP is infrastructure and application independent and tries to handle dynamicity on both levels. MigBSPs results show application performance improvements of up to 16% on dynamic environments while maintaining a small overhead when migrations do not take place.

Metaserver locality and scalability in a distributed NFS

The leveraging of existing storage space in a cluster is a desirable characteristic of a parallel file system. While undoubtedly an advantage from the point of view of resource management, this possibility may face the administrator with a wide variety of alternatives for configuring the file server, whose optimal layout is not always easy to devise. Given the diversity of parameters such as the number of processors on each node and the capacity and topology of the network, decisions regarding the locality of server components like metadata servers and I/O servers have a direct impact on performance and scalability. In this paper, we explore the capabilities of the dNFSp file system on a large cluster installation, observing how scalable the system behaves in different scenarios and comparing it to a dedicated parallel file system. Our obtained results show that the design of dNFSp allows for a scalable and resource-saving configuration for clusters with a large number of nodes.