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Seagate Adopts Helium For a 10TB HDD (computerworld.com)
Lucas123 writes: Seagate has finally adopted helium as an inert gas in its data center drives and has used it to produce a 10TB HDD for cloud-based data centers. Seagate had relied on its shingled magnetic recording technology for high-capacity drives right up until its last 8TB HDD, even after WD has used helium in several iterations of its hermetically sealed, 3.5-in HDDs. The lighter-than-air helium reduces friction on platters and allows more to be used. In Seagate's new HDD, it crammed seven platters 14 heads, a 25% increase in disk density over its 8TB drive.
Against helium? Really? Why do people always feel the need to make worthless, content-free drive-by comments on things they don't understand?
https://www.hgst.com/sites/def...
Still not new or difficult?
In hard drives, the fill gas is used to lift the heads, not for cooling. The idea is that the thin film between the head and platter forms at a shorter distance in helium, so everything can be made smaller and closer together. As another poster pointed out, at room temperature/pressure, helium is monatomic while hydrogen forms H2 molecules, which are larger than the helium atoms.
"Because Science" is one step from "Because old book". Try "Because of my experiment testing my falsifiable assertion".
Heads will crash. The same thing was happening with notebook hard drives on flights because of low atmospheric pressure.
Worked for an measurement instrument company building instruments that had to work in helium atmosphere. We tried for a long time to seal the helium out. Even to the point of filling the entire inside with glass filled epoxy to prevent intrusions of helium. In the end we gave up, and did a redesign to work in helium. solid metal seals will work, but pretty much any other seal will not.
don't cut it off www.mgmbill.org
> These drives will leak.
While technically correct, the rate of static-pressure helium leakage through HGST HelioSeal appears to be measured in decades. They up-rated their enterprise SAS drives from 1.4 million hours MTBF to 2.5 million hours MTBF because hermetically-sealing drives and using helium improves various operating parameters, prolonging life in several ways.
My results in production and the lab bear this out over the past two years: helium drives appear to have substantially lower failure rates than air-filled drives. While nobody has owned a commercial helium drive for a decade yet, the internal helium sensors on the disk farms that I've looked at show no degradation or leakage so far: SMART 22 shows 100.
I'll be watching Seagate's results here with great interest and optimism that their results parallel those of HGST.
Disclaimer: I'm an Oracle employee; my opinions do not necessarily reflect those of Oracle or its affiliates.
Matthew P. Barnson
I learn what I think when I read what I write
The amount of data you can fit in a normal drive would be a good measure. Some googling says the largest 3.5" HDD is 10TB; the largest 3.5" SSD is 16TB.
What matters for the hydrodynamics (drag forces, lift forces on the head) is not directly the size of the molecule, but the molecular mass (related to densitiy of the gas) and the dynamic viscosity (related to both molecular mass and molecular size). The size of the molecule or atom is in any case vanishingly small compared to the distance between the head and the platter. The dynamic viscosities of a few gases at room temperature are: helium is 19 micro-Pa s, air 18 uPa s, and hydrogen 9 uPa s. The molecular masses (proportional to density) are 4, 29, and 2, respectively; this is where helium wins, but hydrogen is better both in molecular mass and viscosity.
The real reason for not using hydrogen gas is that hydrogen (H2) is reactive; at surfaces, it tends to split up into hydrogen atoms (H), which can then diffuse through metals and polymer seals. In the best case, it will leak out within months/years. In the worst case, it will change the crystal lattice and cause material failure. In particular, rare-earth magnents tend to crumble if exposed to hydrogen gas; that's something you really don't want inside a hard disk casing.
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Let me start with an appeal to authority: I actually get paid to do calculations on gas diffusion and pumping of hydrogen.
Depending on the materials of the walls of your helium-containing vessels, drawing a vacuum can take rather long. The point is that diffusive transport is driven by differences in partial pressures (or concentration if the gas is dissolved in a solid). The partial pressure of helium in the atmosphere is about 0.5 Pa; if you have a vessel with a porous wall with 100 kPa of helium (atmospheric pressure) on the inside, then helium will diffuse towards the volume with the lower partial pressure until both sides have the same partial pressure (i.e., 0.5 Pa). The same process will happen in the opposite direction for other gases (nitrogen, oxygen), but at a much slower speed. So at t=0, you have 100 kPa He (pure). After 1 year, you have (for example) 50 kPa He and 0.01 Pa nitrogen. After ten million years, you have 0.5 Pa He and close to 100 kPa nitrogen.
Just imagine that you have a box with a small hole and lot of fruit flies on the inside. Place this box next to a stable where there are lots of big flies. The fruit flies will gradually disappear from the box, but not because they are pushing each other or because the fat flies (that don't fit through the hole) are pushing them out.
Here are the basics of diffusion: https://en.wikipedia.org/wiki/... .
For helium, diffusion speed is proportional to the difference in partial pressures on either side of the wall. For hydrogen, it's more complicated because the hydrogen molecules first need to dissociate before they can permeate through metals; it turns out that the speed of diffusion is driven by the difference in square roots of the partial pressure of hydrogen on either side.
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