Stergios V. Anastasiadis

Learn More
Parallel applications can be executed using the idle computing capacity of workstation clusters. However, it remains unclear how to most effectively schedule the processors among different applications. Processor scheduling algorithms that were successful for shared-memory machines have proven to be inadequate for distributed memory environments due to the(More)
In dynamic environments with frequent content updates, we require online full-text search that scales to large data collections and achieves low search latency. Several recent methods that support fast incremental indexing of documents typically keep on disk multiple partial index structures that they continuously update as new documents are added. However,(More)
Data grids are middleware systems that offer secure shared storage of massive scientific datasets over wide area networks. The main challenge in their design is to provide reliable storage, search, and transfer of numerous or large files over geographically dispersed heterogeneous platforms. The Storage Resource Broker (SRB) is an example of a system that(More)
Parallel application support is one of the ways that have been recently proposed for exploiting the idle computing capacity of workstation networks. However, it has been unclear how to most eeectively schedule the processors among diierent job requests. The distributed memory nature of such environments and the structure of the corresponding applications(More)
Real-time search requires to incrementally ingest content updates and almost immediately make them searchable while serving search queries at low latency. This is currently feasible for datasets of moderate size by fully maintaining the index in the main memory of multiple machines. Instead, disk-based methods for incremental index maintenance substantially(More)
We introduce an algorithm that uses buffer space available at the server for smoothing disk transfers of variable bit-rate streams. Previous smoothing techniques prefetched stream data into the client buffer space, instead. However, emergence of personal computing devices with widely different hardware configurations means that we should not always assume(More)
Explosive growth in online services has recently renewed the interest for building modular and eecient network server systems. System design complications coupled with excessive expectations from technological progress previously discouraged the development of media servers eeciently supporting video streams with variable bit rates. In this paper, we(More)
Scalable network servers are increasingly identified as a critical component in the exponential growth of the Internet. We focus on media servers for variable bit rate streams and study the scalability of alternative disk striping policies, previously known and new. In contrast to results of previous studies, we show that the highest sustained number of(More)
In a system offering on-demand real-time streaming of media files, data striping across an array of disks can improve load balancing, allowing higher disk utilization and increased system throughput. However, it can also cause complete service disruption in the case of a disk failure. Reliability can be improved by adding data redundancy and reserving extra(More)
Whole-file transfer is a basic primitive for Internet content dissemination. Content servers are increasingly limited by disk arm movement given the rapid growth in disk density, disk transfer rates, server network bandwidth, and content size. Individual file transfers are sequential, but the block access sequence on a content server is effectively random(More)