Currently there is a growing interest in using Java for high performance computing. Java has many advantages for high performance computing: it is based on a high-level and object-oriented programming model with support for multithreading and distributed computing. Furthermore, Java 's virtual machine allows applications to run on multiple heterogeneous platforms. A major problem with the use of Java for high performance computing is the I/O. This problem has been solved traditionally in clusters using parallel file systems and parallel I/O libraries, however there is a lack of parallel file systems for Java applications. In this paper, we present a Java parallel I/O library called jExpand. It provides high performance I/O by using several NFS servers in parallel, as NFS can be found in multiple platforms (Linux, Solaris, Windows 2000, etc), we provide a universal parallel file system that can be used everywhere. jExpand requires no changes in the NFS server as it uses RPC operations to provide parallel access to the same file. The paper describes the design, implementation and evaluation of jExpand.

Caching has been intensively used in memory and traditional file systems to improve system performance. However, the use of caching in parallel file systems and I/O libraries has been limited to I/O nodes to avoid cache coherence problems. We specify an adaptive cache coherence protocol that is very suitable for parallel file systems and parallel I/O libraries. This model exploits the use of caching, both at processing and I/O nodes, providing performance improvement mechanisms such as aggressive prefetching and delayed-write techniques. The cache coherence problem is solved by using a dynamic scheme of cache coherence protocols with different sizes and shapes of granularity. The proposed model is very appropriate for parallel I/O interfaces, such as MPI-IO. Performance results, obtained on an IBM SP2, are presented to demonstrate the advantages offered by the cache management methods proposed.

Distributed filesystems are a typical solution in networked environments as clusters and grids. Parallel filesystems are a typical solution in order to reach high performance I/O distributed environment, but those filesystems have some limitations in heterogeneous storage systems. Usually in distributed systems, load balancing is used as a solution to improve the performance, but typically the distribution is made between peer-to-peer computational resources and from the processor point of view. In heterogeneous systems, like heterogeneous clusters of workstations, the existing solutions do not work so well. However, the utilization of those systems is more extended every day, having an extreme example in the grid environment. In this paper we bring attention to those aspects of heterogeneous distributed data systems presenting a parallel file system that take into account heterogeneity of storage nodes, the dynamic addition of new storage nodes, and an algorithm to group requests in heterogeneous systems.

During the last years, Internet video streaming has experiences a phenomenal growth. This is happening despite the notorious difficulties of transmitting data packets with a deadline over the Internet, due to variability in throughput, delays and losses. These problems arise significantly when using wireless networks where the available bandwidth is low and the losses are important due to its error prone transmission nature. In this paper we propose a fast-forwarding technique that is based on segmenting the movie on different files. Normal movie reproduction requires all the files, but fast-forwarding reproduction only requires one file. Those files can me merged by the client or by the server. The segmentation is frame based, grouping all the frames that can be independently decoded together. The resulting file can be showed with any existing player. This group of frames would be the ones to use in a fast-forward reproduction. Our techniques can also be useful in adaptive environments, like wireless networks, because there is no problem for the fast-forward file to use the same optimizations that exist for full movie files. This method also reduces the storage bandwidth and the storage size needed (there is no extra data for fast-forwarding). We also propose a video server architecture that takes advantage of this technique to achieve full interactive video reproduction. The evaluation results shown in this paper demonstrates that our technique enhances video fast-forwarding operations.