Modeling and Performance Evaluation of Cloud On-Ramp by Utilizing a Stochastic Petri-Net

Cloud storage becomes popular, but low data-access performance through WANs (wide area networks) is becoming an issue. A cloud-storage cache, called “cloud on-ramp” (CoR), located at remote offices and connected to the cloud storage at a data center is proposed. Users access the CoR, which stores frequently accessed data as a cache, through a LAN (local area network). In this way, the CoR can improve access performance in case of cache hits; however, delays due to cache misses are a challenge because the data need to be transferred through a WAN. Accordingly, to ensure that applications have reliable access to data (even in the case of a cache miss), a recall method called “partial recall” is proposed. The method is formulated by utilizing a stochastic Petri-net model, and its data access performance improvement is evaluated in comparison with a conventional method through Petri-net simulation.