The cloud storage services are extended with a cloud storage service access protocol that enables users to specify a desired storage tier for each data stream. In response to receiving storage tier specifiers via the protocol, the cloud storage service performs storage operations to identify target storage devices having attributes matching those associated with the requested storage tier. The cloud storage service stores a data stream from the storage client in the identified target storage device associated with the desired storage tier. Storage tiers can be defined based on criteria including capacity costs; access latency; availability; activation state; bandwidth and/or transfer rates; and data replication. The cloud storage service protocol allows data streams to be transferred between storage tiers, storage devices to be activated or deactivated, and data streams to be prefetched and cached. The cloud storage services may charge storage clients based on storage tier use and associated operations.