Earticle

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 software availability model with performance degradation. Assuming that the system can process the multiple tasks simultaneously, we analyze the distribution of the number of tasks whose processes can be completed within the processing time limit with the infinite server queueing model. We derive several software performability measures; these are given as the functions of time and the number of debugging activities. Finally, we illustrate several numerical examples of the measures to investigate the impact of consideration of the performance degradation on the system performability evaluation.

인터넷 기반 시스템에서는 고가용도와 고성능을 제공해야하며, 클러스터 시스템 기술은 이에 대한 하나의 해결책으로 떠오르고 있다. 클러스터 시스템을 사용하는 중요한 목적은 성능과 가용도의 확보에 있으며, 고가용도 클러스터 시스템은 구성 노드들 중 일부에 결함이 발생했을 때 이를 비용ㆍ효율적으로 해결한다. 본 논문은 (n,k) 클러스터 시스템의 성능을 고려한 가용도 개선과 손실비용 분석에 관한 연구로 소프트웨어 재활 기법을 적용한 (n,k) 클러스터 시스템의 가용도 모델을 제안하였으며, 고가용도가 요청되는 시스템에서 소프트웨어 재활은 가용도 향상을 가져오는 유용한 기법 중의 하나임을 파악하였다.

Internet-based computer systems have to provide both high-availability and high-performance. Cluster technology has been used to obtain availability and performance simultaneously Generally, high-availability cluster systems tolerate a failure of a cluster node and cost-effectively solve it. In this paper, we study availability and downtime cost of (n,k) cluster systems. By considering performance, we model state transition of (n,k) cluster systems and apply software rejuvenation technique to improve availability of the system. We find that software rejuvenation can be used to improve availability of (n,k) cluster systems.