Metadata may be stored in, and retrieved from, a scalable, fault-tolerant metadata service. In one example, metadata is divided into partitions, and each partition is served by one or more nodes. For each partition, a first one of the nodes may handle read and write requests, and the other nodes may handle read requests in the event that the first node is down or is experiencing high load. When a request is made with respect to metadata, a metadata server may identify a node, in the partition to which the metadata is assigned, to which the request is to be made. The entity that is making the request then contacts that node, and requests the read or write on the metadata. In a partition, metadata may be replicated between the first node and the other nodes using a log-based replication protocol.