Adam J. Ferrari

Wide area computing: resource sharing on a large scale

Consider almost any computing resource today-whether hardware, software, or data-and it will invariably be networked. Computing over wide area networks has been largely ad hoc, but as needs increase, piecemeal solutions no longer make sense. The authors set out to design and build a wide-area operating system that would allow multiple organizations with diverse platforms to share and combine their resources. This system, Legion, is a network-level operating system designed from scratch to target wide-area computing demands.

JPVM: Network Parallel Computing in Java

The JPVM library is a software system for explicit message-passing based distributed memory MIMD parallel programming in Java. The library supports an interface similar to the C and Fortran interface provided by the Parallel Virtual Machine (PVM) system, but with syntax and semantics modifications afforded by Java and better matched to Java programming styles. The similarity between JPVM and the widely used PVM system supports a quick learning curve for experienced PVM programmers, thus making the JPVM system an accessible, low-investment target for migrating parallel applications to the Java platform. At the same time, JPVM offers novel features not found in standard PVM such as thread safety, multiple communication end-points per task, and default-case direct message routing. JPVM is implemented entirely in Java, and is thus highly portable among platforms supporting some version of the Java Virtual Machine. This feature opens up the possibility of utilizing resources commonly excluded from network parallel computing systems such as Macintosh and Windows-NT based systems. Initial applications performance results achieved with a prototype JPVM system indicate that the Java-implemented approach can offer good performance at appropriately coarse granularities.

A Flexible Security System for Metacomputing Environments

A metacomputing environment is a collection of geographically distributed resources (people, computers, devices, databases) connected by one or more high-speed networks and potentially spanning multiple administrative domains. Security is an essential part of metasystem design -- high-level resources and services defined by the metacomputer must be protected from one another and from possibly corrupted underlying resources, while those underlying resources must minimize their vulnerability to attacks from the metacomputer level. We present the Legion security architecture, a flexible, adaptable framework for solving the metacomputing security problem. We demonstrate that this framework is flexible enough to implement a wide range of security mechanisms and high-level policies.

Support for extensibility and site autonomy in the Legion grid system object model

Grid computing is the use of large collections of heterogeneous, distributed resources (including machines, databases, devices, and users) to support large-scale computations and wide-area data access. The Legion system is an implementation of a software architecture for grid computing. The basic philosophy underlying this architecture is the presentation of all grid resources as components of a single, seamless, virtual machine. Legions architecture was designed to address the challenges of using and managing wide-area resources. Features of the architecture include: global, shared namespaces; support for heterogeneity; security; wide-area data sharing; wide-area parallel processing; application-adjustable fault tolerance; efficient scheduling and comprehensive resource management. We present the core design of the Legion architecture, with focus on the critical issues of extensibility and site autonomy. Grid systems software must be extensible because no static set of system-level decisions can meet all of the diverse, often conflicting, requirements of present and future user communities, nor take best advantage of unanticipated future hardware advances. Grid systems software must also support complete site autonomy, as resource owners will not turn control of their resources over to a dictatorial system.

Heterogeneous process state capture and recovery through Process Introspection

The ability to capture the state of a process and later recover that state in the form of an equivalent running process is the basis for a number of important features in parallel and distributed systems. Adaptive load sharing and fault tolerance are well-known examples. Traditional state capture mechanisms have employed an external agent (such as the operating system kernel) to examine and capture process state. However, the increasing prevalence of heterogeneous cluster and “metacomputing” systems as high-performance computing platforms has prompted investigation of process-internal state capture mechanisms. Perhaps the greatest advantage of the process-internal approach is the ability to support cross-platform state capture and recovery, an important feature in heterogeneous environments. Among the perceived disadvantages of existing process-internal mechanisms are poor performance in multiple respects, and difficulty of use in terms of programmer effort. In this paper we describe a new process-internal state capture and recovery mechanism: Process Introspection. Experiences with this system indicate that the perceived disadvantages associated with process-internal mechanisms can be largely overcome, making this approach to state capture an appropriate one for cluster and metacomputing environments.

Multiparadigm distributed computing with TPVM

Distributed concurrent computing based on lightweight processes can potentially address performance and functionality limits in heterogeneous systems. The TPVM framework, based on the notion of ‘exportable services’, is an extension to the PVM message-passing system, but uses threads as units of computing, scheduling, and parallelism. TPVM facilitates and supports three different distributed concurrent programming paradigms: (a) the traditional, task based, explicit message-passing model; (b) a data-driven instantiation model that enables straightforward specification of computation based on data dependencies; and (c) a partial shared-address space model via remote memory access, with naming and typing of distributed data areas. The latter models offer significantly different computing paradigms for network-based computing, while maintaining a close resemblance to, and building upon, the conventional PVM infrastructure in the interest of compatibility and ease of transition. The TPVM system comprises three basic modules: a library interface that provides access to thread-based distributed concurrent computing facilities, a portable thread interface module which abstracts the required thread-related services, and a thread server module which performs scheduling and system data management. System implementation as well as applications experiences have been very encouraging, indicating the viability of the proposed models, the feasibility of portable and efficient threads systems for distributed computing, and the performance improvements that result from multithreaded concurrent computing.

Failure-Resilient Computations in the EcliPSe System

Local or wide-area connected workstation cluster-based computation systems are inherently failure-prone, particularly for long running computations. In this work we introduce a variety of features for failure resilience in the EcliPSe system for replicative applications. Key characteristics of fault-tolerant EcliPSe are ease of use, low statesaving costs, system scalability and good performance.