Moving data among a plurality of non-volatile storage devices of a storage device includes accumulating credits at each of a plurality of periodic intervals for separate portions of the devices, wherein the credits correspond to a wear rating for each of the devices, reducing credits for each of the portions at each of the periodic intervals based on an amount of data written to each of the portions during each of the intervals, on the wear rating for each of the devices, and on a percent life used for the devices, and moving data from a first one of the portions having a relatively low amount of credits to a second one of the portions having a relatively high amount of credits. The devices may be solid state drives. The wear rating may be a drive writes per day rating provided by a manufacture of the solid state drive.