Why don't all drive makers (both solid state and rotating) use a RAID-like structure to offer drives with any speed or reliability level that buyers want? Seems like it could be much more efficient to put RAID into the drive than to wrap it around multiple physical drives. Maybe it would actually decrease reliability (you lose all the storage if part of it goes out and you can't replace component drives)? It seems like it would be a way to get large permanent storage that is as fast as SRAM, which has been a holy grail in computing for a long time, to get past the CPU I/O bandwidth bottleneck presented by slower drives.