Hard Glass Spinner Technology: HGST's new 2.5-incher Hitachi GST has announced the Charles Atlas of small format disk drives, a 1.2TB drive spinning at 10,000rpm. Aren't such drives supposed to be getting driven off the beach by SSD bullies? Charles Atlas No they are not. It's the 15,000rpm drives that are suffering from the flash raiders, up in 3.5-inch format land. Down here …
aah, I remember the clatter and whoosh from my 10mb attached to my B+. Awesome. And expensive. And still didn't the stop the thargoids pwning my ass, every time my hyperspace failed. Which was a lot.
And naturally, this was the good ol' days when stuff was still counted in multiples of 1024...
How brittle is the substrate compared to the more typical metal ones? Since this is aimed a laptops, I wondered what the likelihood of smashing one was.
Obviously, the damage to the heads would be fatal in either model, but recovery would be even harder if you've got to rebuild four platters from shards first.
It can't be too brittle, or the repeated spin up/down forces would weaken it over time. It will still need to flex and warp a little (even if we're talking microscopic deviations from flat). Also, it would help with natural vibration/resonation inherent in spinning media that isn't contactless, and then there is the heat cycles to worry about.
Safe to say, it should be plenty robust enough. When they start talking about using recycled cardboard as platter is when you should worry.
Glass is actually very strong if it is made correctly. "Glass" simply means the atoms of a substance are in a high state of disorder - it's not a crystal where the atoms are very orderly. The highly disordered state means there are no cleavage planes between crystals, so the are no places for a break to start.
The glass most of us are familiar with - window glass - is actually made weaker by design: tempered glass has a great deal of stress built in, so that if it does break, it breaks into a bazillion small, relatively not-so-sharp pieces, so as to not slice you like a baloney. Were it not for that stress, it would be much stronger, but would break into large, sharp guillotine-like pieces that have a nasty tendency to open veins and remove limbs.
For more information, look up "met-glass" or "amorphous metal" for a description of making metals like steel in this highly disordered state.
Does nobody else remember Pilkington's corporate-image advert with the glass hammer being used on a nail? And even more strikingly at the end, the glass claw of the hammer being used to lever out the bent nail?
My candidate for best corporate-image ad ever. Sadly, it couldn't save Pilkington from the French.
Glass, even the everyday sort, is very strong but brittle, meaning if a crack gets started it will spread catastrophically. A disk platter is of necessity perfectly polished, and installed in a very benign environment where there's nothing to scratch it (which is how cracks get started), meaning glass is an ideal substrate. In passing, it's metals that crack up after repeated flexing. Glasses don't. Flexing glass either breaks it first time, or not at all (provided it's perfectly micro-crack-free to start with and there's nothing to scratch it in service).
Tempered glass isn't deliberately weakened. It's cooled in a way that builds in a compressive stress to its surface (strengthened) at the cost of tension in its core (a disintegration waiting to happen). A tiny scratch or crack in the compressed zone won't spread in response to everyday flexing or temperature changes. But if a crack is ever driven through that zone into the core, the object instantly tears itself into small (and desirably un-sharp) pieces.
Transparent aluminium, you say? Check out No. 2.
So basically this is an exercise in fitting 10lbs of sh*t in a 5lb bag.
Why not go to a 10lb bag and go back to full height drives? I can stick 14 drives in my case, but my motherboard wouldn't like supporting that. I'd be happier with 2 or 4 larger (taller) high capacity drives.
Why not go to a 10lb bag and go back to full height drives
Because a disk drive is an example of something that works better miniaturized. The smaller the platter, the faster it can spin without disintegrating or distorting. The smaller the arm carrying the head, the less it flexes and vibrates, so the faster the settling time after a seek. Both mean that a 2.5 inch datacentre disk has intrinsically lower latency than a 3.5 inch one.
It's like how a flea can accelerate itself at 300G, whereas it takes a lot less to make a human go squishy.
Also you don't need so much energy to move smaller head assemblies, so the drive generates less vibration to upset its neighbouring drives. With tens or hundreds packed close together, this is yet another advantage. I've heard tell of homebrew servers with four desktiop drives bolted into a single metal cage, that degraded quite atrociously under heavy loads. Those rubber drive-mount grommets in the better full-tower cases are definitely not just for show. They provide vibration isolation between drives.
Vibration is also the reason why a big stack of many tens of platters in a full-height enclosure wouldn't work well, if at all.
I wonder how long before we see the 1.8 inch datacentre drive? The one disadvantage of a smaller drive is smaller capacity, but 1Tb is more than enough in many applications.
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