1. A method of controlling storage of content on a storage device, the method comprising: in a storage device having a controller in communication with non-volatile memory, wherein the non-volatile memory comprises a first type of non-volatile memory and a second type of non-volatile memory, the controller: receiving data for storage in the non-volatile memory; upon determining that a fullness of the storage device has reached a proactive defragmentation threshold, only writing sequentially addressed logical groups of received data to the second type of non-volatile memory; and upon determining that the fullness of the storage device has reached a reactive defragmentation threshold automatically defragmenting data already written into the second type of non-volatile memory in response to a triggering event.