1. A computer-implemented method for simulating a state of a distributed storage system having a plurality of instances, comprising: at a computer system including one or more processors and memory storing one or more programs for execution by the one or more processors: obtaining a current state of the distributed storage system and replication policies for objects in the distributed storage system, 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; 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.