A technique for determining when to destage write data from a fast, NVS of a computer system from an upper level to a lower level of storage in the computer system comprises adaptively varying a destage rate of the NVS according to a current storage occupancy of the NVS; maintaining a high threshold level for the NVS; maintaining a low threshold level that is set to be a predetermined fixed amount below the high threshold; setting the destage rate of the NVS to zero when the NVS occupancy is below the low threshold; setting the destage rate of the NVS to be maximum when the NVS occupancy is above the high threshold; linearly increasing the destage rate of the NVS from zero to maximum as the NVS occupancy goes from the low to the high threshold; and adaptively varying the high threshold in response to a dynamic computer storage workload.