A system for load-balancing partitions of file servers of a file storage service of a cloud computing system is provided. The system collects latency information relating to access requests to access storage that is partitioned. The access requests are processed by the file servers. Each file server is assigned partitions, which are indexes to the storage. For each file server, the system generates, from the latency information, partition statistics relating to partition latency associated with each partition assigned to that file server. For each partition, the system applies rules to the statistics to determine actions to take to mitigate performance problems. Each rule has a condition and an action. When the condition of the rule is satisfied based on the partition statistics for the partition, the system records an indication to take the action of the rule.