The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

Farnam Jahanian - One of the best experts on this subject based on the ideXlab platform.

  • A real-time primary-backup Replication Service
    IEEE Transactions on Parallel and Distributed Systems, 1999
    Co-Authors: Hengming Zou, Farnam Jahanian
    Abstract:

    This paper presents a real-time primary-backup Replication scheme to support fault-tolerant data access in a real-time environment. The main features of the system are fast response to client requests, bounded inconsistency between primary and backup, temporal consistency guarantee for replicated data, and quick recovery from failures. The paper defines external and interobject temporal consistency, the notion of phase variance, and builds a computation model that ensures such consistencies for replicated data deterministically where the underlying communication mechanism provides deterministic message delivery semantics and probabilistically where no such support is available. It also presents an optimization of the system and an analysis of the failover process which includes failover consistency and failure recovery time. An implementation of the proposed scheme is built within the x-kernel architecture on the MK 7.2 microkernel from the Open Group. The results of a detailed performance evaluation of this implementation are also discussed.

  • SRDS - Optimization of a real-time primary-backup Replication Service
    Proceedings Seventeenth IEEE Symposium on Reliable Distributed Systems (Cat. No.98CB36281), 1998
    Co-Authors: Hengming Zou, Farnam Jahanian
    Abstract:

    The primary-backup Replication model is one of the commonly adopted approaches to providing fault tolerant data Services. Its extension to the real time environment, however, imposes the additional constraint of timing predictability, which requires a bounded overhead for managing redundancy. The paper discusses the trade-off between reducing system overhead and increasing (temporal) consistency between the primary and backup, and explores ways to optimize such a system to minimize either the inconsistency or the system overhead while maintaining the temporal consistency guarantees of the system. An implementation built on top of the existing RTPB model (H. Zou and F. Jahanian, 1998) was developed within the x-kernel architecture on the Mach OSF platform running MK 7.2. Results of an experimental evaluation of the proposed optimization techniques are discussed.

  • Design and evaluation of a window-consistent Replication Service
    IEEE Transactions on Computers, 1997
    Co-Authors: A Mehra, Jennifer Rexford, Farnam Jahanian
    Abstract:

    Real-time applications typically operate under strict timing and dependability constraints. Although traditional data Replication protocols provide fault tolerance, real-time guarantees require bounded overhead for managing this redundancy. This paper presents the design and evaluation of a window-consistent primary-backup Replication Service that provides timely availability of the repository by relaxing the consistency of the replicated data. The Service guarantees controlled inconsistency by scheduling update transmissions from the primary to the backup(s); this ensures that client applications interact with a window-consistent repository when a backup must supplant a failed primary. Experiments on our prototype implementation, on a network of Intel-based PCs running RT-Mach, show that the Service handles a range of client loads while maintaining bounds on temporal inconsistency.

  • design and evaluation of a window consistent Replication Service
    Real Time Technology and Applications Symposium, 1995
    Co-Authors: A Mehra, Jennifer Rexford, Hocksiong Ang, Farnam Jahanian
    Abstract:

    Real-time applications typically operate under strict timing and dependability constraints. Although traditional data Replication protocols provide fault tolerance, real-time guarantees require bounded overhead for managing this redundancy. This paper presents the design and evaluation of a window-consistent primary-backup Replication Service that provides timely availability of the repository by relaxing the consistency of the replicated data. The Service guarantees controlled inconsistency by scheduling update transmissions from the primary to the backup(s); this ensures that client applications interact with a window-consistent repository when a backup must supplant a failed primary. Experiments on our prototype implementation show that the Service handles a range of client loads while maintaining bounds on temporal inconsistency.

  • IEEE Real Time Technology and Applications Symposium - Design and evaluation of a window-consistent Replication Service
    Proceedings Real-Time Technology and Applications Symposium, 1995
    Co-Authors: A Mehra, Jennifer Rexford, Hocksiong Ang, Farnam Jahanian
    Abstract:

    Real-time applications typically operate under strict timing and dependability constraints. Although traditional data Replication protocols provide fault tolerance, real-time guarantees require bounded overhead for managing this redundancy. This paper presents the design and evaluation of a window-consistent primary-backup Replication Service that provides timely availability of the repository by relaxing the consistency of the replicated data. The Service guarantees controlled inconsistency by scheduling update transmissions from the primary to the backup(s); this ensures that client applications interact with a window-consistent repository when a backup must supplant a failed primary. Experiments on our prototype implementation show that the Service handles a range of client loads while maintaining bounds on temporal inconsistency.

Jahanianfarnam - One of the best experts on this subject based on the ideXlab platform.

Hengming Zou - One of the best experts on this subject based on the ideXlab platform.

  • A real-time primary-backup Replication Service
    IEEE Transactions on Parallel and Distributed Systems, 1999
    Co-Authors: Hengming Zou, Farnam Jahanian
    Abstract:

    This paper presents a real-time primary-backup Replication scheme to support fault-tolerant data access in a real-time environment. The main features of the system are fast response to client requests, bounded inconsistency between primary and backup, temporal consistency guarantee for replicated data, and quick recovery from failures. The paper defines external and interobject temporal consistency, the notion of phase variance, and builds a computation model that ensures such consistencies for replicated data deterministically where the underlying communication mechanism provides deterministic message delivery semantics and probabilistically where no such support is available. It also presents an optimization of the system and an analysis of the failover process which includes failover consistency and failure recovery time. An implementation of the proposed scheme is built within the x-kernel architecture on the MK 7.2 microkernel from the Open Group. The results of a detailed performance evaluation of this implementation are also discussed.

  • SRDS - Optimization of a real-time primary-backup Replication Service
    Proceedings Seventeenth IEEE Symposium on Reliable Distributed Systems (Cat. No.98CB36281), 1998
    Co-Authors: Hengming Zou, Farnam Jahanian
    Abstract:

    The primary-backup Replication model is one of the commonly adopted approaches to providing fault tolerant data Services. Its extension to the real time environment, however, imposes the additional constraint of timing predictability, which requires a bounded overhead for managing redundancy. The paper discusses the trade-off between reducing system overhead and increasing (temporal) consistency between the primary and backup, and explores ways to optimize such a system to minimize either the inconsistency or the system overhead while maintaining the temporal consistency guarantees of the system. An implementation built on top of the existing RTPB model (H. Zou and F. Jahanian, 1998) was developed within the x-kernel architecture on the Mach OSF platform running MK 7.2. Results of an experimental evaluation of the proposed optimization techniques are discussed.

Bettina Schnor - One of the best experts on this subject based on the ideXlab platform.

  • Service Replication in grids ensuring consistency in a dynamic failure prone environment
    International Parallel and Distributed Processing Symposium, 2008
    Co-Authors: Andre Luckow, Bettina Schnor
    Abstract:

    A major challenge in a Service-oriented environment as a Grid is fault tolerance. The more resources and Services involved, the more complicated and error-prone becomes the system. Migol (Luckow and Schnor, 2008) is a Grid middleware, which addresses the fault tolerance of Grid applications and Services. Migol's core component is its registry Service called application information Service (AIS). To achieve fault tolerance and high availability the AIS is replicated on different sites. Since a registry is a stateful Web Service, the Replication of the AIS is no trivial task. In this paper, we present our concept for active Replication of Grid Services. Migol's Replication Service uses a token-based algorithm and certificate-based security to provide secure group communication. Further, we show in different experiments that active Replication in a real Grid environment is feasible.

Hanspeter Schwefel - One of the best experts on this subject based on the ideXlab platform.

  • dependability evaluation of a Replication Service for mobile applications in dynamic ad hoc networks
    International Service Availability Symposium, 2008
    Co-Authors: Erling Vestergaard Matthiesen, Ossama Hamouda, Mohamed Kaâniche, Hanspeter Schwefel
    Abstract:

    In order to increase availability and reliability of stateful applications, redundancy as provided by Replication in cluster solutions is a well-known and frequently utilized approach. For mobile Services in dynamic ad-hoc networks, such Replication mechanisms have to be adapted to deal with the frequently higher communication delays and with the intermittent connectivity. Dynamic clustering strategies in which the replica set is adjusted to the current network state can help to handle the network dynamicity. The paper develops a stochastic Petri net model (and its corresponding Markov chain representation) to analyze the resulting availability and replica consistency in such dynamic clusters. The numerical results are interpreted in the context of a vehicular (c2c) communication use-case and can be used to determine optimized cluster configuration parameters.

  • ISAS - Dependability evaluation of a Replication Service for mobile applications in dynamic ad-hoc networks
    Service Availability, 2008
    Co-Authors: Erling Vestergaard Matthiesen, Ossama Hamouda, Mohamed Kaâniche, Hanspeter Schwefel
    Abstract:

    In order to increase availability and reliability of stateful applications, redundancy as provided by Replication in cluster solutions is a well-known and frequently utilized approach. For mobile Services in dynamic ad-hoc networks, such Replication mechanisms have to be adapted to deal with the frequently higher communication delays and with the intermittent connectivity. Dynamic clustering strategies in which the replica set is adjusted to the current network state can help to handle the network dynamicity. The paper develops a stochastic Petri net model (and its corresponding Markov chain representation) to analyze the resulting availability and replica consistency in such dynamic clusters. The numerical results are interpreted in the context of a vehicular (c2c) communication use-case and can be used to determine optimized cluster configuration parameters.