A storage appliance comprising: a first solid state drive, SSD, and a second SSD configured to store data; a controller; and a mapping table configured to record the location of the stored data; wherein the controller is configured to: calculate a first utilization parameter based on a total amount of utilized data on the first SSD and a second utilization parameter based on a total amount of utilized data on the second SSD; if the first utilization parameter is less than a threshold and the second utilization parameter exceeds the threshold: identify a data range of data stored on the first SSD to be removed, wherein the removal of the identified data range from the first SSD causes the first utilization parameter based on the total amount of utilized data on the first SSD to exceed the threshold, and migrate the data corresponding to the identified data range from the first SSD to the second SSD, wherein the first utilization parameter based on a total amount of utilized data on the first SSD is increased by the migration of the data and causes an increase in spare area in the first SSD; wherein the controller is further configured to determine, using the mapping table, the location of the data corresponding to the identified data range to be removed from the first SSD, and wherein the controller is further configured to calculate the first utilization parameter and second utilization parameter by querying the mapping table to determine which LBAs on each SSD have been written to and which have not. a first solid state drive, SSD, and a second SSD configured to store data; a controller; and a mapping table configured to record the location of the stored data; wherein the controller is configured to: calculate a first utilization parameter based on a total amount of utilized data on the first SSD and a second utilization parameter based on a total amount of utilized data on the second SSD; if the first utilization parameter is less than a threshold and the second utilization parameter exceeds the threshold: identify a data range of data stored on the first SSD to be removed, wherein the removal of the identified data range from the first SSD causes the first utilization parameter based on the total amount of utilized data on the first SSD to exceed the threshold, and migrate the data corresponding to the identified data range from the first SSD to the second SSD, wherein the first utilization parameter based on a total amount of utilized data on the first SSD is increased by the migration of the data and causes an increase in spare area in the first SSD; calculate a first utilization parameter based on a total amount of utilized data on the first SSD and a second utilization parameter based on a total amount of utilized data on the second SSD; if the first utilization parameter is less than a threshold and the second utilization parameter exceeds the threshold: identify a data range of data stored on the first SSD to be removed, wherein the removal of the identified data range from the first SSD causes the first utilization parameter based on the total amount of utilized data on the first SSD to exceed the threshold, and migrate the data corresponding to the identified data range from the first SSD to the second SSD, identify a data range of data stored on the first SSD to be removed, wherein the removal of the identified data range from the first SSD causes the first utilization parameter based on the total amount of utilized data on the first SSD to exceed the threshold, and migrate the data corresponding to the identified data range from the first SSD to the second SSD, wherein the first utilization parameter based on a total amount of utilized data on the first SSD is increased by the migration of the data and causes an increase in spare area in the first SSD; wherein the controller is further configured to determine, using the mapping table, the location of the data corresponding to the identified data range to be removed from the first SSD, and wherein the controller is further configured to calculate the first utilization parameter and second utilization parameter by querying the mapping table to determine which LBAs on each SSD have been written to and which have not.