Performance and availability assessment for the configuration of distributed workflow management systems

Abstract. Workflow management systems (WFMSs) that are geared for the orchestration of enterprise-wide or even “virtual-enterprise”-style business processes across multiple organizations are complex distrib-uted systems. They consist of multiple workflow engines, application servers, and ORB-style communication servers. Thus, deriving a suit-able configuration of an entire distributed WFMS for a given applica-tion workload is a difficult task. This paper presents a mathematically based method for configuring a distributed WFMS such that the application's demands regarding per-formance and availability can be met while aiming to minimize the total system costs. The major degree of freedom that the configuration method considers is the replication of the underlying software compo-nents, workflow engines and application servers of different types as well as the communication server, on multiple computers for load parti-tioning and enhanced availability. The mathematical core of the method consists of Markov-chain models, derived from the application's workflow specifications, that allow assessing the overall system's per-formance, availability, and also its performability in the degraded mode when some server replicas are offline, for given degrees of replication. By iterating over the space of feasible system configurations and as-sessing the quality of candidate configurations, the developed method determines a configuration with near-minimum costs