Data storage technologies for years have been going in one direction – data carriers needed to be ever smaller, with ever larger storage capacity, as well as energy-efficiency (economical), and fast. You cannot have everything at once, of course, but miracles do happen and sometimes an idea appears in line with the famous Apple slogan “think different”. The creator of shingled magnetic recording certainly thought differently.
Until recently there was only one answer to the question of how to store more data on a carrier: create ever thinner recording tracks and cram them in tighter and tighter. This method seemed to be not only right, but also the only one possible. Technological progress which allowed the creation of ever thinner magnetic heads, which record and delete data, made it possible to create more and more capacious carriers, without the need to look for alternative solutions. However, eventually technology reached a limit imposed by the laws of physics. You cannot shrink the head ad infinitum, since the smaller the distance between the opposite poles, the smaller the magnetic field that is created. If the field is too weak, it won’t be able to write and delete data. The technological boundary, limiting the width of the recording track, is 25 nm. The newest data carriers using perpendicular recording create tracks that are 50-30 nm wide – therefore coming very close to the boundaries that cannot be crossed.
In accordance with the principle of approaching problems in an unconventional manner, there appeared the concept of shingled magnetic recording (SMR). Just as with roof tiles, where subsequent rows of shingles partially overlap the previous row, so it is with the recording of tracks where two tracks can also overlap. This technology allows for the use of a relatively wide head, which records an (also relatively) wide track, which – in turn – is partially overlapped by the following track. The whole concept hinges on the fact that during recording the important bytes of information get written on the part of the track that doesn’t get overlapped. Thanks to this new approach, we can create tightly adhering tracks of important data, which limits the loss of space that occurs during traditional recording.
The new technology allows for the use of relatively wide (and therefore strong) heads – of about 90 nm – which eventually create readable data tracks that are 10nm wide, hence considerably below the technological boundary of perpendicular recording. Obviously the technology has its limitations. The efficiency of use is a considerable problem. In particular, recording and erasing of individual data is not possible without rewriting the whole block of data. For now, however, this direction seems to be the only practical solution wherever storing large amounts of data is of the essence.