Automatic Recovery Mechanisms Research Articles

An Imperfect Fault Coverage Model With Coverage of Irrelevant Components

This paper addresses the coverage (including identification and isolation) of irrelevant components in systems with imperfect fault coverage (IFC). In fault-tolerant systems, a single not-covered component fault may thwart the automatic recovery mechanisms, and lead to a system or subsystem failure. The models that consider the effects of IFC are known as coverage models (CMs). In traditional CMs, except those considering functional dependency (a similar concept to relevancy but with different assumptions and semantics), coverage is typically limited to faulty components regardless of their relevancies. Consequently, an operational but irrelevant component will not be isolated, and may threaten the system by its future uncovered (not-covered) failures. Although the system is generally assumed to be coherent, which implies the relevancy of each component in the initial system state, the traditional CMs do not consider the fact that an initially relevant component could become irrelevant after the failures of other components. We propose the irrelevancy coverage model (ICM) to cover the irrelevant components in addition to the faulty components. In the ICM, a component will be isolated from the system whenever it becomes irrelevant (even it is not failed), such that its future not-covered failures will not affect the system anymore. By incorporating the coverage of irrelevant components, the ICM opens up a new cost-effective approach to improve system reliability without additional redundancy.

3-Hierarchical resource management model on web grid service architecture

In this paper, we developed a framework for efficient resource management within the grid service environment. For considering the grid service architecture and functions, the resource management is the most important to grid service; therefore, GridRMF (Grid Resource Management Framework) is modeled and developed in order to respond to such variable characteristics of resources as accordingly as possible. GridRMF uses the participation level of grid resource as a basis of its hierarchical management. This hierarchical management divides managing domains into two parts: VMS (Virtual Organization Management System) for virtual organization management and RMS (Resource Management System) for metadata management. VMS mediates resources according to optimal virtual organization selection mechanism, and responds to malfunctions of the virtual organization by LRM (Local Resource Manager) automatic recovery mechanism. RMS, on the other hand, responds to load balance and fault by applying resource status monitoring information into adaptive performance-based task allocation algorithm.

A separable method for incorporating imperfect fault-coverage into combinatorial models

This paper presents a new method for incorporating imperfect FC (fault coverage) into a combinatorial model. Imperfect FC, the probability that a single malicious fault can thwart automatic recovery mechanisms, is important to accurate reliability assessment of fault-tolerant computer systems. Until recently, it was thought that the consideration of this probability necessitated a Markov model rather than the simpler (and usually faster) combinatorial model. SEA, the new approach, separates the modeling of FC failures into two terms that are multiplied to compute the system reliability. The first term, a simple product, represents the probability that no uncovered fault occurs. The second term comes from a combinatorial model which includes the covered faults that can lead to system failure. This second term can be computed from any common approach (e.g. fault tree, block diagram, digraph) which ignores the FC concept by slightly altering the component-failure probabilities. The result of this work is that reliability engineers can use their favorite software package (which ignores the FC concept) for computing reliability, and then adjust the input and output of that program slightly to produce a result which includes FC. This method applies to any system for which: the FC probabilities are constant and state-independent; the hazard rates are state-independent; and an FC failure leads to immediate system failure.

Proactive anomaly detection using distributed intelligent agents

Proactive network anomaly detection is crucial to provide quality of service guarantees for future networks. We characterize a set of proactively detectable anomalies in terms of the management information base variables. The time series data obtained from these variables are analyzed by an intelligent agent, which is a simple and lightweight signal processor. The agent provides real-time proactive alarms that are indicative of impending network problems and suggests the possibility of implementing automatic recovery mechanisms. Proactive detection was accomplished within minutes. The agent is shown to be amenable to distributed implementation, and is a promising approach to self-managed networks.

Bidirectional fibre optic loop-structured network

A basic bidirectional fibre optic loop-structured network configuration which provides an automatic recovery mechanism against a line failure and employs WDM-TDMA techniques for signal multiplexing is presented. Experimental results of a prototype of such a network are also described.