Input/output (I/O) activity in the multiple tier storage system is monitored to collect statistical information. The statistical information is recurrently transformed into an exponential moving average (EMA) of the I/O activity having a predefined smoothing factor. Data portions in the multiple tier storage system are sorted into buckets of varying temperatures corresponding to the EMA. At least one data migration plan is recurrently generated for matching the sorted data portions to at least one of an available plurality of storage device classes. One data portion sorted into a higher temperature bucket is matched with a higher performance storage device class of the available plurality of storage device classes than another data portion sorted into a lower temperature bucket.