A system for performing auto-tiering is disclosed. The system may include a plurality of storage devices offering a plurality of resources and organized into storage tiers. The storage devices may store data for virtual machines. A receiver may receive I/O commands and performance data for the virtual machines. A transmitter may transmit responses to the I/O commands. An auto-tiering controller may select storage tiers to store the data for the virtual machines and may migrate data between storage tiers responsive to the performance data. The selection of the storage tiers may optimize the performance of all virtual machines across all storage tiers, factoring the change in performance of the virtual machines and a migration cost to migrate data between storage tiers.