4 ms·

Any sense of how much helium will permeate through the grain structure of the drive enclosure during its lifetime?

by boxcardavin 10y ago

JohnJamesRambo 10y ago
Does helium go through metal?
- astrodust 10y ago
  No seal is ever perfect, that's the concern. Plus helium, being monatomic, is able to jam into tinier holes than things like oxygen, nitrogen, or water vapour.
  - TheOtherHobbes 10y ago
    I've asked people who used the first gen He drives because it's an obvious worry, and the consensus seems to be that they're at least as reliable as conventional drives. MTBF doesn't seem unusually bad, and can even be better than some trad designs.
    - Nition 10y ago
      This is different than the typical failure scenario though, isn't it? You might have a few drives with bad seals that fail early. But say the majority are sealed properly, but the helium still leaks out at x small rate over time, you might have almost all the drives suddenly fail at around the same time after say 6 years or whatever. I don't think you can really know if they're truly reliable in that sense until you can take one that's been sitting one in a drawer for 10 years and plug it in.
      - astrodust 10y ago
        A company like Backblaze is bound to find out before the consumers do but I have a feeling it'll be fine. Keeping gas inside of something isn't much harder than keeping it sealed enough that dust stays out. A high-altitude environment might put more pressure on the seals than other places, that could shorten the life-span, but other than that it shouldn't be a huge deal. Most drives have a commercial life-span of no more than 4-6 years anyway. After that you're on borrowed time.
  - bleair 10y ago
    I've been wondered exactly this about the He filled drives. Should I just assume that after 4 years the drive is not going to work? 8 years? I am aware that in 4 years modern drives of the same cost will be at least 4x the capacity, but still it's my data on the drive that I care about.
- nialo 10y ago
  Helium does go through metal, although even in this case the amount is probably insignificant. Helium also goes through whatever the sealing gasket is made from, at a much higher rate. http://lpc1.clpccd.cc.ca.us/lpc/tswain/permeation.pdf http://lpc1.clpccd.cc.ca.us/lpc/tswain/permeation.pdf is a neat chart, probably the gasket is buna-n because it's cheap. I think that chart and https://en.wikipedia.org/wiki/Permeation https://en.wikipedia.org/wiki/Permeation are enough to get an order of magnitude answer to OP's question, but I'm not quite up to doing the math. Serious vacuum systems have to worry about this sort of thing more than one might expect. I once had a project where two test engineers and myself spent around a week hunting for leaks in a vacuum system that turned out to be caused by my specifying Silicone o-rings instead of Viton.
  - zkms 10y ago
    > probably the gasket is buna-n because it's cheap No. Helium hard drives are laser-welded shut. See http://www.seagate.com/files/www-content/product-content/enterprise-hdd-fam/enterprise-capacity-3-5-hdd-10tb/_shared/docs/helium-drive-launch-tp686-1-1602us.pdf http://www.seagate.com/files/www-content/product-content/ent... for the details about what parts are made out of what and the basic details of fabrication.
    - nialo 10y ago
      That is really cool, thanks for the link. I should apparently make fewer assumptions. I'm not sure why I thought there was a rubber seal, I have vague memories of seeing an exploded view with one somewhere.

Any sense of how much helium will permeate through the grain structure of the drive enclosure during its lifetime?

JohnJamesRambo 10y ago

Does helium go through metal?

astrodust 10y ago
No seal is ever perfect, that's the concern. Plus helium, being monatomic, is able to jam into tinier holes than things like oxygen, nitrogen, or water vapour.
- TheOtherHobbes 10y ago
  I've asked people who used the first gen He drives because it's an obvious worry, and the consensus seems to be that they're at least as reliable as conventional drives. MTBF doesn't seem unusually bad, and can even be better than some trad designs.
  - Nition 10y ago
    This is different than the typical failure scenario though, isn't it? You might have a few drives with bad seals that fail early. But say the majority are sealed properly, but the helium still leaks out at x small rate over time, you might have almost all the drives suddenly fail at around the same time after say 6 years or whatever. I don't think you can really know if they're truly reliable in that sense until you can take one that's been sitting one in a drawer for 10 years and plug it in.
    - astrodust 10y ago
      A company like Backblaze is bound to find out before the consumers do but I have a feeling it'll be fine. Keeping gas inside of something isn't much harder than keeping it sealed enough that dust stays out. A high-altitude environment might put more pressure on the seals than other places, that could shorten the life-span, but other than that it shouldn't be a huge deal. Most drives have a commercial life-span of no more than 4-6 years anyway. After that you're on borrowed time.
- bleair 10y ago
  I've been wondered exactly this about the He filled drives. Should I just assume that after 4 years the drive is not going to work? 8 years? I am aware that in 4 years modern drives of the same cost will be at least 4x the capacity, but still it's my data on the drive that I care about.
nialo 10y ago
Helium does go through metal, although even in this case the amount is probably insignificant. Helium also goes through whatever the sealing gasket is made from, at a much higher rate. http://lpc1.clpccd.cc.ca.us/lpc/tswain/permeation.pdf http://lpc1.clpccd.cc.ca.us/lpc/tswain/permeation.pdf is a neat chart, probably the gasket is buna-n because it's cheap. I think that chart and https://en.wikipedia.org/wiki/Permeation https://en.wikipedia.org/wiki/Permeation are enough to get an order of magnitude answer to OP's question, but I'm not quite up to doing the math. Serious vacuum systems have to worry about this sort of thing more than one might expect. I once had a project where two test engineers and myself spent around a week hunting for leaks in a vacuum system that turned out to be caused by my specifying Silicone o-rings instead of Viton.
- zkms 10y ago
  > probably the gasket is buna-n because it's cheap No. Helium hard drives are laser-welded shut. See http://www.seagate.com/files/www-content/product-content/enterprise-hdd-fam/enterprise-capacity-3-5-hdd-10tb/_shared/docs/helium-drive-launch-tp686-1-1602us.pdf http://www.seagate.com/files/www-content/product-content/ent... for the details about what parts are made out of what and the basic details of fabrication.
  - nialo 10y ago
    That is really cool, thanks for the link. I should apparently make fewer assumptions. I'm not sure why I thought there was a rubber seal, I have vague memories of seeing an exploded view with one somewhere.