My thesis investigates how to replicate services using the primary-backup approach in grid environments. First, the design of a primary-backup protocol using the OGSI grid standard and implementation based on Globus Toolkit 3 are presented, in order to evaluate the feasibility and performance of existing grid middlewares. Then an architecture of integrating the primary-backup replication with other techniques is proposed and evaluated. Finally, this thesis addressing the issue replicating services on asynchronous grid environments. The experiments on local clusters and PlanetLab show the protocols we proposed provide good performance for replicating grid services

"Group communications systems" have been designed to provide an infrastructure for fault-tolerance in distributed systems, including wide-area systems. In our work on master-worker computation for GriPhyN, which is a large project in the area of the computational grid, we asked the question "should we build our wide-area master-worker computation using wide-area group communications?" This paper explains why we decided doing so was not a good idea.

Pre-2018 CSE ID: CS2002-0725

Service Oriented Architectures (SOAs) are gaining increased use and interest with the growing importance of web and grid services, and the dependability of services in such architectures is critical. While the techniques for implementing highly dependable services are well known, each technique has its tradeoffs relative to runtime performance overhead, resource cost, and level of assurance provided. The ability to choose the dependability based on the service requirements and characteristics allows the optimization of these tradeoffs. The goal of our work is to provide mechanisms that allow different durability mechanisms (e.g., in-memory replication or database storage) to be implemented as separate modules and then applied as needed to different variables and data structures constituting the service state. We describe an overall architecture that allows such durability customization for each web service and present preliminary performance results.

Pre-2018 CSE ID: CS2006-0861

The living cell possesses extraordinary molecular and biochemical mechanisms by which to recognize and efficiently remove foreign, damaged, or denatured proteins. This essential function has been a barrier to the overexpression of recombinant proteins in most expression systems. A notable exception is the overexpression in E. coli of recombinant proteins, most of which, however, end-up as "inclusion bodies", i.e., cytoplasmic aggregates of proteins that are inaccessible to the cell's proteasome. "Fusion constructs as protein overexpression vectors" proved to be unparalleled in their ability to cause substantial accumulation of recombinant proteins from plants, animals, and bacteria, as soluble proteins in unicellular cyanobacteria. Recombinant protein levels in the range of 10-20% of the total cellular protein can be achieved. The present work investigated this unique property in the context of recombinant protein stability in Synechocystis sp. PCC 6803 by developing and applying an in vivo cellular tobacco etch virus cleavage system with the objective of separating the target heterologous proteins from their fusion leader sequences. The work provides new insights about the overexpression, cellular stability, and exploitation of transgenes with commercial interest, highly expressed in a cyanobacterial biofactory. The results support the notion that eukaryotic plant- and animal-origin recombinant proteins are unstable, when free in the cyanobacterial cytosol but stable when in a fusion configuration with a highly expressed cyanobacterial native or heterologous protein. Included in this analysis are recombinant proteins of the plant isoprenoid biosynthetic pathway (isoprene synthase, β-phellandrene synthase, geranyl diphosphate synthase), the human interferon protein, as well as prokaryotic proteins (tetanus toxin fragment C and the antibiotic resistance genes kanamycin and chloramphenicol). The future success of synthetic biology approaches with cyanobacteria and other systems would require overexpression of pathway enzymes to attain product volume, and the work reported in this paper sets the foundation for such recombinant pathway enzyme overexpression.