1. A solid-state storage subsystem comprising: a non-volatile memory array; a write cache for temporarily storing data to be written to the non-volatile memory array; a controller configured to: implement a data redundancy configuration with a plurality of data stripes in the non-volatile memory array; move data stored in the write cache to the non-volatile memory array, the data being moved in a size increment matching a pre-defined size of the data stripes in the data redundancy configuration; and in response to detecting a start of a shutdown of the storage subsystem, move data in the write cache to the non-volatile memory array to create a partial data stripe that is smaller than the pre-defined stripe size when a quantity of the cached data is insufficient to create a data stripe of the pre-defined size, thereby reducing an amount of power needed to enable the controller to move data in the write cache to the non-volatile memory array.