Fog Computing infrastructures have been proposed as an alternative to Cloud Computing to provide computing with low latency for the Internet of Things (IoT). A few storage systems have been proposed to store data in those infrastructures. Most of them are relying on a Distributed Hash Table (DHT) to store the location of objects which is not efficient because the node storing the location of the data may be placed far away from the object replicas. In this paper, we propose to replace the DHT by a tree-based approach mapping the physical topology. Servers look for the location of an object by requesting successively their ancestors in the tree. Location records are also relocated close to the object replicas not only to limit the network traffic when requesting an object, but also to avoid an overload of the root node. We also propose to modify the Dijkstra’s algorithm to compute the tree used. Finally, we evaluate our approach using the object store InterPlanetary FileSystem (IPFS) on Grid’5000 using both a micro experiment with a simple network topology and a macro experiment using the topology of the French National Research and Education Network (RENATER). We show that the time to locate an object in our approach is less than 15 ms on average which is around 20% better than using a DHT.