In a distributed Video-on-Demand system, the customers of the service are in charge of storing the video catalog, and they actively participate in serving video requests generated by other customers. The design of such systems is driven by key constraints like customers' upload and storage capacity, video popularity distribution, and so on. In this paper, by means of extensive simulations we analyze the impact of: i) the video allocation technique used for distributed storage ii) the use of cache to allow nodes to re-distribute the video they are downloading iii) the use of static/dynamic algorithms for video distribution. Based on these results, we provide some guidelines for setting the system parameters. We show that the use of cache strongly improves system performance while allocation techniques based on predicted video popularity can be sensitive and bring little improvement. Dynamic distribution algorithms are needed only in extreme scenarios while static ones are commonly sufficient.