1. A method comprising: obtaining data about an aggregation of storage devices with respect to a specified time period; determining, with the obtained data about the aggregation of storage devices, a total amount of data transferred for the aggregation of storage devices over the specified time period, input/output performance capability of the aggregation of storage devices, and utilization of the storage devices for servicing requests by the aggregation of storage devices over the specified time period; determining an aggregate demand value that represents demand on the aggregation of storage devices based on the obtained data, wherein said determining the aggregate demand value comprises determining a product of the utilization of the storage devices for servicing requests by the aggregation of storage devices over the specified time period and a quotient of the total amount of data transferred for the aggregation of storage devices over the specified time period and the input/output performance capability of the aggregation of storage devices and; determining demand on logical storage containers of the aggregation of storage devices; and using the determined demand on the logical storage containers of the aggregation of storage devices to manage the aggregation of storage devices.