A method for dynamically balancing the allocation of data among a plurality of physical data storage devices having a plurality of RAID devices defined thereon, wherein at least one of the plurality of RAID devices is comprised of at least one of a different type of physical storage device or a different number of physical data storage devices than at least one other of the plurality of RAID devices, includes determining a usage factor unique to each RAID device and balancing data I/O based at least in part on the usage factor.