This application relates to load balancing for a number of partitions of a network-based storage service. Each partition includes a number of server devices and/or network devices located in a data center and configured to provide access to storage resources hosted within the data center. User accounts are assigned to a particular partition such that requests related to a particular user account are routed to that partition. Periodically, a load balancing algorithm is executed to re-assign user accounts to different partitions to rebalance resource consumption across the different partitions. The load balancing algorithm can balance resource consumption for any number of resource types by generating a vector of resource utilization parameters for each user account, sorting the plurality of user accounts into clusters based on the vectors, and mapping at least some user accounts to different partitions.