A Study of Costs and Benefits of Content Sharing in Personal Cloud Storage

摘要

Personal Cloud Storage (PCS) is a very popular Internet service. In addition to backup, PCS allows content sharing among multiple devices, which is a valuable functionality for many users. Yet maintaining a PCS service incurs both storage and bandwidth costs to service providers, as the update and successive downloads of shared files may generate extra traffic on the PCS cloud servers. This becomes particularly worrisome as a large fraction of users (e.g., over 90%) does not pay for the service, joining a free version with limited storage capacity but typically without content sharing restrictions. Thus, a natural concern arises on the costs and benefits of such service, for both provider and users. In this paper, we propose a model to analyze the cost-benefit tradeoffs of content sharing in PCS services for both parties. Our model uses a macroeconomic concept, notably user surplus, to capture the satisfaction of different classes of users, as well as a cost saving function to capture the interest of the provider in reducing bandwidth costs. We use our model to evaluate two alternative policies to the content sharing architecture in use in existing PCS services, searching for scenarios in which both parties have benefits. The proposed policies rely on incentives given to users in exchange of their participation to offload shared content from cloud servers. Our investigation, based on analytical modeling and data-driven experiments, shows that the incentive leads to greater satisfaction to both parties, and that the alternative policies can reach scenarios which benefit both provider and users, with reductions in provider's bandwidth costs by 20% and increases in user satisfaction from 51 to 82% under reasonable model assumptions.