Of the planar optical storage techniques, the one most appropriate for PetaFLOPS systems is the optical disk technology with a potential capacity approaching 100 gigabits and a data transfer rate as high as 10 megabytes per second; however, like magnetic disk technology, it suffers from a relatively slow access time (milliseconds), due to the reliance on mechanical motion. Although there has been research into optoelectronic and acoustooptic scanning of planar media, the systems continue to consist of a rotating medium being addressed by a single optical head.
Because PetaFLOPS systems will require large throughput of data, optical disk systems must increase the readout data rate. This may be accomplished by employing parallel readout, a solution whose time has probably arrived. If the bits to be read out in parallel are stored adjacent to one another in some rectangular or circular area, a single laser beam can be used to illuminate this area, and the bits can be read out in parallel via a two-dimensional photodetector array. If the bits can not be stored in such a regular pattern, the optical addressing may be accomplished by using a free-space interconnect system as was described above.