1. A non-transitory computer readable storage medium storing one or more programs configured for execution by a computer, the one or more programs comprising instructions for: obtaining a current state of the distributed storage system and replication policies for objects in the distributed storage system, wherein the distributed storage system includes a plurality of instances, and wherein a respective replication policy for a respective object specifies criteria for placing copies of the respective object among the plurality of instances; receiving one or more proposed modifications to the state of the distributed storage system, wherein each respective proposed modification to the state of the distributed storage system includes a respective time at which the respective proposed modification to the state of the distributed storage system is to occur; simulating the state of the distributed storage system over time based on the current state of the distributed storage system, one or more current statistical trends in the state of the distributed storage system, the replication policies for the objects in the distributed storage system, and the proposed modifications to the state of the distributed storage system; and generating one or more reports relating to the simulation.