It is necessary to have the precise definition of available performance of high availability systems that can represent the availability and performability of the systems altogether. However, the difference between numeric scales of availability and performance metrics such as waiting time makes quantitative evaluation difficult. A number of previous studies on availability do not include a per...

A new model composer is proposed to automatically generate non-anonymous model replicas in the context of performability and dependability evaluation. It is a state-sharing composer that extends the standard anonymous replication composer in order to share the state of a replica among a set of other specific replicas or among the replica and another external model. This new composition operator...

This paper discusses software performability evaluation considering the real-time property. We assume that the software system has two operational states from the viewpoint of the end users: one is operating with the desirable performance level according to specification and the other is with degraded performance level. The time-dependent behavior of the system is described by the Markovian sof...

Exceptions constitute a widely accepted fault tolerance mechanism, suitable to manage both hardware and software faults. In performability analysis it is a common practice to exploit software tools capable of describing a system using models expressed in various formalisms. Often these tools provide extensibility features that allow augmenting the primitives of a given formalism, but in most ca...

Quantitative system evaluation concerning both software design faults and hardware operational faults has not yet received enough attention. Although a few studies considered such dependability analysis, analytic evaluation of systems with integrated software and hardware fault tolerance remains a challenge. In particular, the need to distinguish the effects of software design faults from those...

An adaptive scheme for software fault-tolerance is evaluated from the point of view of performability, comparing it with previously published analyses of the more popular schemes, recovery blocks and multiple version programming. In the case considered, this adaptive scheme, "Self-Configuring Optimistic Programming" (SCOP), is equivalent to N-version programming in terms of the probability of d...

Response Time as a Performability Metric for Online Services

This paper describes a measurement-based performability model based on error and resource usage data collected on a multiprocessor system. A method for identifying the model structure is introduced and the resulting model is validated against real data. Model development from the collection of raw data to the estimation of the expected reward is described. Both normal and error behavior of the ...