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"Usage of helium inside a hard drive helps to reduce the drag force acting on the spinning disk stack and lower the fluid flow forces affecting the disks and th

by woodman 10y ago

"Usage of helium inside a hard drive helps to reduce the drag force acting on the spinning disk stack and lower the fluid flow forces affecting the disks and the heads. As a result, HDD makers can install up to seven platters into a standard drive and also use lower-power motors and mechanics. This reduces the power consumption of the HDDs."

donatj 10y ago
Would nitrogen not? What about a vacuum then?
- cataflam 10y ago
  Nitrogen is pretty close to air, which is already 80% nitrogen. The gain would be minimal. As for vacuum, it's harder to maintain, and wouldn't work anyway : https://news.ycombinator.com/item?id=11593997 https://news.ycombinator.com/item?id=11593997
- b101010 10y ago
  "Disk drives depend on the head floating on a cushion of air, they are not designed to operate in a vacuum" https://en.wikipedia.org/wiki/Flying_height https://en.wikipedia.org/wiki/Flying_height
  - XorNot 10y ago
    I've always found that odd these days. Given that we're already not doing dumb magnetic manipulation anymore, is it not feasible to use a static magnetic field between the head and platter to the cushion the drive at all? The magnetic interaction with the platter would be presumably predictable, since it's the oscillation that's used to write the data.
- gambiting 10y ago
  Considering that normal hard drives have regular in them, and regular air is over 78% nitrogen, I guess bumping it to 100% nitrogen wouldn't make any difference.
- raverbashing 10y ago
  I would guess viscosity of a fluid is a function of atomic weight and intermolecular forces, both are higher in N2 than in He
- Grishnakh 10y ago
  Nitrogen = air. Around 77% of air is nitrogen, much of the rest of oxygen, then some CO2, and the rest is trace gases. You don't get any improvement in most things by using pure nitrogen instead of air, unless one of those other gases was causing you a problem (in the case of tires, oxygen degrades the materials the tires are made of). The point of helium is that its molecules are much smaller and lighter than that of regular air so there's less friction. You don't get that with nitrogen. You would get it with hydrogen though (which is quite a bit smaller even than helium), though there's probably some other problem with H2 that prevents that. And yeah, a vacuum should be ideal; the problem there is probably that atmospheric pressure, at 14.7psi (IIRC) is pretty significant, strong enough to hold your suction-cup-mounted cellphone to your car windshield, so you have to have a pretty robust hard drive enclosure to maintain that vacuum without crushing. Vacuum chambers are usually really beefy. It would be interesting to see a vacuum hard drive; I wonder if WD ever tried that, just to see what it could do. They probably just can't make it and stick with the regular 2.5" or 3.5" form factors. Maybe a double-height 3.5" size (with the internals being the same size as a regular 3.5" drive, the rest just being extra structure) would be possible.

by woodman 10y ago

donatj 10y ago

Would nitrogen not? What about a vacuum then?

cataflam 10y ago
Nitrogen is pretty close to air, which is already 80% nitrogen. The gain would be minimal. As for vacuum, it's harder to maintain, and wouldn't work anyway : https://news.ycombinator.com/item?id=11593997 https://news.ycombinator.com/item?id=11593997
b101010 10y ago
"Disk drives depend on the head floating on a cushion of air, they are not designed to operate in a vacuum" https://en.wikipedia.org/wiki/Flying_height https://en.wikipedia.org/wiki/Flying_height
- XorNot 10y ago
  I've always found that odd these days. Given that we're already not doing dumb magnetic manipulation anymore, is it not feasible to use a static magnetic field between the head and platter to the cushion the drive at all? The magnetic interaction with the platter would be presumably predictable, since it's the oscillation that's used to write the data.
gambiting 10y ago
Considering that normal hard drives have regular in them, and regular air is over 78% nitrogen, I guess bumping it to 100% nitrogen wouldn't make any difference.
raverbashing 10y ago
I would guess viscosity of a fluid is a function of atomic weight and intermolecular forces, both are higher in N2 than in He
Grishnakh 10y ago
Nitrogen = air. Around 77% of air is nitrogen, much of the rest of oxygen, then some CO2, and the rest is trace gases. You don't get any improvement in most things by using pure nitrogen instead of air, unless one of those other gases was causing you a problem (in the case of tires, oxygen degrades the materials the tires are made of). The point of helium is that its molecules are much smaller and lighter than that of regular air so there's less friction. You don't get that with nitrogen. You would get it with hydrogen though (which is quite a bit smaller even than helium), though there's probably some other problem with H2 that prevents that. And yeah, a vacuum should be ideal; the problem there is probably that atmospheric pressure, at 14.7psi (IIRC) is pretty significant, strong enough to hold your suction-cup-mounted cellphone to your car windshield, so you have to have a pretty robust hard drive enclosure to maintain that vacuum without crushing. Vacuum chambers are usually really beefy. It would be interesting to see a vacuum hard drive; I wonder if WD ever tried that, just to see what it could do. They probably just can't make it and stick with the regular 2.5" or 3.5" form factors. Maybe a double-height 3.5" size (with the internals being the same size as a regular 3.5" drive, the rest just being extra structure) would be possible.