1. A computer-implemented method, comprising: receiving a write request from a client to write a data block to a distributed data storage system, wherein the write request includes a colocation hint that identifies a colocation group associated with the data block, wherein the distributed data storage system situates copies of data blocks associated with the colocation group in the same data centers when possible; and in response to the write request, using the colocation hint to identify one or more data centers associated with the colocation group, and writing copies of the data block to the one or more identified data centers.