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WD Announces 8TB, 10TB Helium Hard Drives
Lucas123 writes: Western Digital's HGST subsidiary today announced it's shipping its first 8TB and the world's first 10TB helium-filled hard drive. The 3.5-in, 10TB drive also marks HGST's first foray into the use of shingled magnetic recording technology, which Seagate began using last year. Unlike standard perpendicular magnetic recording (PMR), where data tracks rest side by side, SMR overlaps the tracks on a platter like shingles on a roof, thereby allowing a higher areal density. Seagate has said SMR technology will allow it to achieve 20TB drives by 2020. That company has yet to use helium, however. HGST said its use of hermetically-sealed helium drives reduces friction among moving drive components and keeps dust out. Both drives use a 7-platter configuration with a 7200 RPM spindle speed. The company said it plans to discontinue its production of air-only drives by 2017, replacing all data center models with helium drives.
The most important question is what is the lifespan of the helium containment. Helium is notorious for getting in to and out of places that other elements can't. For example, in balloon borne cosmic ray experiments, or anything with a calorimeter or hodoscope that utilizes photomultiplier tubes, you have the problem of the helium from the balloon getting into the PMTs, which hold a vacuum. Of course, there are low pressure conditions to consider, but I'm still skeptical of the helium staying in the hard drive.
No, there are not. In this case, low molecular weight is the key, and that nearly rules out anything except H2 and He.
H2 is too reactive though. Ne is interesting, but even more expensive the He and the only advantage is less leaking.
N2 is not meaningfully different from normal air, and Ar is even heavier.
CH4 is cheap, light, and mostly unreactive (at moderate temps) but it's really not light enough to compete with He.
And that's the end of the list.
I was also wondering this. Wouldn't nitrogen or argon/neon be cheaper?
The point of using helium is NOT that it is inert, but that it is low density (although the inertness is also nice). Neon is five times as dense and far more expensive. Methane is four times the density. The only gas lighter would be hydrogen. But hydrogen has a nasty habit of migrating through metal, leaking out, and embrittling the metal in the process. Low density gases reduce friction both through reduced mass, and a higher speed threshold for laminar (rather than turbulent) flow. Low density gases tend to also be better heat conductors, helping to keep the disk cool. That is why high density gases, like xenon or sulfer hexafloride, are used in insulated windows.
In the late 1960s, DDC of San Diego made head-per-track disk drives that operated with a helium atmosphere. These units had a cylinder of helium fastened to the baseplate (the units were 19" rack mount), and the documentation included procedures for replacing the cylinder and for purging from a full-sized cylinder if it was ever necessary to open the unit for repairs.
I had driven down to San Diego circa 1978 to buy a cylinder of refill helium from DDC for one of these in a hand-me-down system, but never got around to replacing the cylinder on the drive. The cylinder sat in my garage for years. Thirty years later I was a returned adult physics student. My professor was using a similar helium cylinder to purge a cryostat for a superconducting magnet. He ran out of helium, and the department had no other helium. I told him "wait 20 minutes, I'll be back." I retrieved the cylinder from my garage, and the professor was both delighted and baffled. When connected to the regulator, the cylinder proved to have maintained a remarkable fraction of its original pressure, and the professor was able to complete his procedure. Sadly, another part of the magnet failed and suffered a gas pressure explosion as it was being cooled.
In a remarkable coincidence, I noted that the department's helium cylinder and mine were identical, all the way down to a part number stenciled on them.