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Comment by rusbus | Hacker News Reader

Can someone comment as to why it needs to be filled with helium?

From the actual article:

"... but HGST's use of helium, which offers significantly less air resistance to the spinning platters, is probably the main one."

Lower air resistance/friction and lower turbulence for the heads.

So, what will happen if it leaks? Will it just get slow or stop working?

It will probably stop working. Aerodynamics are crucial to the way a hard disk works. One cannot not simply increase the density of the gas inside the drive by 10x and expect it to continue working.

The helium reduces resistance which results in lower vibration of the read/write heads, which in turn allows for reduced space between the platters and the heads, which allows for a reduced space between the platters and more platters per drive. If the same drive was filled with air rather than helium, the increased vibration of the heads would cause them to crash into the platters - which would scrub the disk clean (which would be bad).

why it can't be vacuumed?

In a vacuum, the head would crash into the platter. The gas provides a cushion. Flying height these days is something like 3nm (yes, you read that right), so the tiniest vibration could cause a head crash in a vacuum.

Sure, but at say 1/10th atm Nitrogen would seem to work. So, the question becomes why is helium significantly better?

> at say 1/10th atm Nitrogen would seem to work

But then you have to have a case strong enough not to bend under the pressure difference.

At 1 atm, of course, helium has much lower density (and therefore lower viscosity). Nitrogen weighs 28 g/mol; helium just 4 g/mol.

So in measurements of standard helium rubber party balloons, how many drives could one fill with Helium from one such balloon?

What about Hydrogen? Too reactive with metals?

Very much so: https://en.wikipedia.org/wiki/Hydrogen_embrittlement And it's generally reactive stuff.

Helium is a nice, nonreactive noble gas.

> Flying height these days is something like 3nm (yes, you read that right), so the tiniest vibration could cause a head crash in a vacuum.

Wikipedia goes on to say the head could crash into a fingerprint or _smoke particle! So... how did my spinning rust laptop drive ever survive on my lap?

A HEPA or the like quality air filter to equalize air pressure, which doesn't pass much air anyway.

The heads need a gas of some sort to float on.

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