Your flying companion
The development of hard disks have been just amazing, the price per MB has fallen every year. If you crash it and take a look inside you will see one or more very smooth brownish platters and a mechanical device with one or more arms. Pricing for mechanics and platters have been constant, so you roughly paid the same for the box, but you have got more storage and capacity. In my collection of 2,5”:s during the last 10 years I have: 0.7, 4, 40, 200 and now 450GB on my current laptop I bought a year ago. The last five years I have never managed to fill them up before I bought a new one. I never clean up anymore, which is a pity… Though I still remember my 10MB (10MB, 85ms, 0.5MB/s) from my first PC-XT in 1985. I also remember good old 3340 (70MB, 25ms and 0.9MB/s) from the seventies, which you could look at picked out of the box and 3380 (2,5GB, 16ms, 3MB/s) – where the platter went into a sealed dark room that could not be opened. The comparison between mainframe and PC disks were $100k/2500MB = $40/MB – $2k/10MB = $200/MB, so it was still cheaper to store in a mainframes and with much better performance in the eighties.
But matters have changed in 30 years …100$/750GB = 0,001$/MB, 7200rpm and 100MB/s. But I was unable to find the access time… The rotation have not changed to much during this period and the speed of the arms have not changed dramatically. BUT the package of bits, areal density, is the explanation behind the speed of getting data into the computer and the price per MB, which you can see in the graph to the left, the scale on the y-axis is logarithmic!! So things have happened.
But what happens inside that dark box. Each morning it is the same procedure as every day, a boring travel seen from the perspective of a disk head, staring up any version of Windows – how much fun is that?. You wake him up and the day starts, exactly the same travel every morning!! A new boring(?) day he thinks, I am not so sure about that. Flying up from the landing zone, let us see things from this perspective. OK, flying(?) well there are about 10-20 molecules of air between him and the surface, flying? Around 3nm and maybe a little bit higher is where he flies in 120km/h in my computer (7200rpm) or double speed if in a high performance drive. That is risk taking in my view! Most dramatic flying I have ever seen was in Budapest 1st of May 2004 when Hungary was celebrating entrance into EU, then I saw a guy flying under the Chain Bridge. I hope you see him!!! I don’t know the exact height of that flight, 20 m maybe in 300 km/h??? But that is a gap, isn’t it compared to say lower than10nm in 120km/h!! Well you say, it is all about surface smoothness isn’t it? Yeah, that was what I thought at least. It must be OK, if the surface is smooth enough. So I asked “How smooth is it?” and I “Googled”.. It is no easy question to answer, it is all about “nanodefects” was what I learned. Really nothing you could see or feel. Our visible light can’t see these things, it is a matter about wavelength and resolution, you need “Rontgen-eyes” to see, so either my disk head has that or is he just a flying in blindness like a bat? Looking into details a dust gain would look like Ayers Rock in that perspective, flying like in Budapest, but in blindness. Don’t worry just take a look at the mathematical theory behind this, it is no miracle. The rules of physics (hydrodynamic lubrication) tells you this is what happens there, nothing to worry about, he just flies over the rock, at least most of the time… as is easily seen in the formulas. So don’t worry you will probably do well if you take your backup tomorrow.
Here is a listing of some of the links inspiring me: