A method for controlling dispatching work tasks in a multi-tier storage environment. A computer system receives storage demands of work tasks. The computer system determines placement and migration policies for data in storage tiers in a storage system. The computer system prepares the storage tiers for meeting the storage demands of work tasks, based on the placement and migration policies. The computer system determines a state of preparation of the storage tiers for meeting the storage demands of work tasks. The computer system determines a list including work tasks that can proceed and work tasks that cannot proceed, based on the state of the preparation. The computer system modifies a schedule of the work tasks, based on the list.