FADI: a fault-tolerant environment for open distributed computing

FADI is a complete programming environment that serves the reliable execution of distributed application programs. FADI encompasses all aspects of modern fault-tolerant distributed computing. The built-in user-transparent error detection mechanism covers processor node crashes and hardware transient failures. The mechanism also integrates user-assisted error checks into the system failure model. The nucleus non-blocking checkpointing mechanism combined with a novel selective message logging technique delivers an efficient, low-overhead backup and recovery mechanism for distributed processes. FADI also provides means for remote automatic process allocation on the distributed system nodes

Efficient checkpointing over local area networks

Parallel and distributed computing on clusters of workstations is becoming very popular as it provides a cost effective way for high performance computing. In these systems, the bandwidth of the communication subsystem (Using Ethernet technology) is about an order of magnitude smaller compared to the bandwidth of the storage subsystem. Hence, storing a state in a checkpoint is much more efficient than comparing states over the network. In this paper we present a novel checkpointing approach that enables efficient performance over local area networks. The main idea is that we use two types of checkpoints: compare-checkpoints (comparing the states of the redundant processes to detect faults) and store-checkpoints (where the state is only stored). The store-checkpoints reduce the rollback needed after a fault is detected, without performing many unnecessary comparisons. As a particular example of this approach we analyzed the DMR checkpointing scheme with store-checkpoints. Our main result is that the overhead of the execution time can be significantly reduced when store-checkpoints are introduced. We have implemented a prototype of the new DMR scheme and run it on workstations connected by a LAN. The experimental results we obtained match the analytical results and show that in some cases the overhead of the DMR checkpointing schemes over LAN's can be improved by as much as 20%

CSP channels for CAN-bus connected embedded control systems

Closed loop control system typically contains multitude of sensors and actuators operated simultaneously. So they are parallel and distributed in its essence. But when mapping this parallelism to software, lot of obstacles concerning multithreading communication and synchronization issues arise. To overcome this problem, the CT kernel/library based on CSP algebra has been developed. This project (TES.5410) is about developing communication extension to the CT library to make it applicable in distributed systems. Since the library is tailored for control systems, properties and requirements of control systems are taken into special consideration. Applicability of existing middleware solutions is examined. A comparison of applicable fieldbus protocols is done in order to determine most suitable ones and CAN fieldbus is chosen to be first fieldbus used. Brief overview of CSP and existing CSP based libraries is given. Middleware architecture is proposed along with few novel ideas

Autonomous Fault-Tolerant Avionics for Small COTS Satellites: to Reality and Prototype

In this contribution we present practical experiences from realizing a prototype of the first truly fault-tolerant and autonomously operating avionics suite for miniaturized satellite down to the size of a 2U CubeSat. Our initial demonstrator setup consists of a mix of COTS parts and FPGA development boards, which we gradually expanded in scope and capabilities. After four iterations of PCB development and manufacturing, we have condensed this design to a fully integrated custom PCB-based prototype. Our fourth architecture iteration is stackable and is designed to fit on an 80×80mm PCB footprint. It is furthermore capable of operating as generic satellite subsystem node, functioning in a distributed, fault-tolerant, interconnected manner together with other subsystems. Each node is fully replaceable by two or more neighboring subsystem-nodes. In consequence, we achieve a satellite bus setup which is in spirit similar to integrated modular avionics and modern fault-tolerant avionics network architectures used in other fields. We realize this setup through a high-speed chip-to-chip network in a compact CubeSat form factor

SpiNNaker: Fault tolerance in a power- and area- constrained large-scale neuromimetic architecture

AbstractSpiNNaker is a biologically-inspired massively-parallel computer designed to model up to a billion spiking neurons in real-time. A full-fledged implementation of a SpiNNaker system will comprise more than 105 integrated circuits (half of which are SDRAMs and half multi-core systems-on-chip). Given this scale, it is unavoidable that some components fail and, in consequence, fault-tolerance is a foundation of the system design. Although the target application can tolerate a certain, low level of failures, important efforts have been devoted to incorporate different techniques for fault tolerance. This paper is devoted to discussing how hardware and software mechanisms collaborate to make SpiNNaker operate properly even in the very likely scenario of component failures and how it can tolerate system-degradation levels well above those expected

The Raincore Distributed Session Service for Networking Elements

Motivated by the explosive growth of the Internet, we study efficient and fault-tolerant distributed session layer protocols for networking elements. These protocols are designed to enable a network cluster to share the state information necessary for balancing network traffic and computation load among a group of networking elements. In addition, in the presence of failures, they allow network traffic to fail-over from failed networking elements to healthy ones. To maximize the overall network throughput of the networking cluster, we assume a unicast communication medium for these protocols. The Raincore Distributed Session Service is based on a fault-tolerant token protocol, and provides group membership, reliable multicast and mutual exclusion services in a networking environment. We show that this service provides atomic reliable multicast with consistent ordering. We also show that Raincore token protocol consumes less overhead than a broadcast-based protocol in this environment in terms of CPU task-switching. The Raincore technology was transferred to Rainfinity, a startup company that is focusing on software for Internet reliability and performance. Rainwall, Rainfinity’s first product, was developed using the Raincore Distributed Session Service. We present initial performance results of the Rainwall product that validates our design assumptions and goals