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What Is the Purpose of the “Do Not Cover This Hole” Hole on Hard Drives?

From tiny laptop hard drives to beefier desktop models, traditional disk-based hard drives have a very bold warning on them: DO NOT COVER THIS HOLE. What exactly is the hole and what terrible fate would befall you if you covered it?

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites.

The Question

SuperUser reader oKtosiTe noticed the warning label and needed to get to the bottom of things:

On many hard drives, there’s a text warning to “not cover this hole”, sometimes adding that doing so will void the warranty.

What is the purpose of this hole and why would covering it cause damage or increase the likelihood of drive failure?

Thankfully no field studies or warranty voiding were required to solve the mystery.

The Answer

Image courtesy of SuperUser contributor Oliver Salzburg.

SuperUser contributor music2myear offers some insight into the tiny hole and the importance of leaving it unobstructed:

It allows for equalization of air pressure between the inside and outside of the drive. While it is not a complete pass-through of outside air into the HDD internals, there is a filter inside the hole that allows the air pressure to equalize.

If the drive were completely sealed, operating at altitudes significantly different from those the drive was manufactured and sealed at, it would cause problems and increase the likelihood of catastrophic failures.

This system works in much the same way as the Eustachian tubes that allow our ears internal pressures to equalize, preventing the explosion of our ear drums.

Dennis expands on this explanation by directing us towards the section of Wikipedia dealing with hard drive integrity:

Check out the Wikipedia hard drive entry paying attention to the Integrity section with reference to the “breather hole”:

Hard disk drives require a certain range of air pressures in order to operate properly. The connection to the external environment and pressure occurs through a small hole in the enclosure (about 0.5 mm in breadth), usually with a filter on the inside (the breather filter). If the air pressure is too low, then there is not enough lift for the flying head, so the head gets too close to the disk, and there is a risk of head crashes and data loss. Specially manufactured sealed and pressurized disks are needed for reliable high-altitude operation, above about 3,000 m (9,800 ft).[99] Modern disks include temperature sensors and adjust their operation to the operating environment. Breather holes can be seen on all disk drives—they usually have a sticker next to them, warning the user not to cover the holes.

The mere mention of headcrashes (and the horrible memory of the sounds our last lost-to-head-crash drive made) are more than enough warning for us.


Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Jason Fitzpatrick is warranty-voiding DIYer and all around geek. When he's not documenting mods and hacks he's doing his best to make sure a generation of college students graduate knowing they should put their pants on one leg at a time and go on to greatness, just like Bruce Dickinson. You can follow him on if you'd like.

  • Published 10/26/12

Comments (17)

  1. David

    You can always take a dead one apart and find the filter…

  2. mgo

    If you cover that hole, the little pixie that scurries about inside that tiny silver box looking for your files would suffocate.

  3. wagonman

    I recently moved to the tropics and one morning found small ants crawling out of my laptop.
    Could these be the cause of my next catastrophe?

  4. beergas

    I think it’s there to mop up coffee spills the keyboard misses. Not seeing one on my SSD SATA III.
    hmm Maybe it’s defective so best type fast. Praying it lasts until flash drives get really cheap & large enough for Windows 19 w/ ThoughtPad.

  5. Vinh

    Soon, standard HDD’s won’t have air holes as they will be filled with Helium. Htachi (WD) plans on shipping them next year.
    http://www.xbitlabs.com/news/storage/display/20120913091202_Western_Digital_s_Division_Announces_Helium_Filled_Hard_Drive_Platform.html

  6. Reader

    The reason your SSD does not have a hole is that SSDs don’t have mechanical components, thus no need to keep the container tightly sealed and at an even temperature.

  7. Milt

    A serious question:

    I sometimes stay at close to 9,000 feet on ski trips to Colorado, and use my laptop at these altitudes. Am I risking a higher probability a disk crash because of the thin air. I’ve never used it above the 3,000 meters listed in the Wikipedia article, but I’m sure it isn’t a hard and fast altitude at which the drive goes from no failure to always fail. Any further information would be welcomed.

  8. Acclimate

    The correct word here is “acclimate”.
    Showing results for acclimate
    ac·cli·mate/ˈakləˌmāt/
    Verb:
    1.Become accustomed to a new climate or to new conditions.

  9. Joel Lewis

    Actually the correct word is “acclimatise.” “Acclimate” is a word Americans made up, not least because they can’t spell “acclimatise” and would insist on putting a “z” (that’s a ‘zed’ not a ‘zee’) in place of the ‘s’.

  10. Whatever

    I think at this point, now that the United States have been separated from Great Britain for so long, that we can all understand how and why there are differences in spelling and form of different words.

    I was also able to understand the article just fine with the author’s choice of words.

    My only regret is that the two comments above mine drove me to add this third and equally as pointless commentary to question: What made those comments necessary or productive? Let’s all grow up here.
    (I am fully aware of the irony of this post. I maintain that it still makes my point)

  11. Jon S

    At higher altitude operations you’d expect the price per GB to be on par with SSDs and take the latter route.

  12. Gregg

    Correct use of grammar and of words is important, and correcting a mistake is productive, IF a mistake has actually been made, and if that mistake actually affected the reader’s understanding. In this case both the comment by Acclimate and by Joel Lewis are incorrect (nowhere in the article was the correct word “acclimate”, and Lewis’s UK-ism is flat out wrong on every point–acclimate is the more original form, and acclimation rather than acclimatization is preferable in the U.K.) and thus neither contributes to the reader’s understanding of the article.

  13. krokkenoster

    Guys which language does MAKE SENSE? Exceptions are the rule and there are NO hard and fast rules that can in every case be applied

  14. Merlynson

    I put snot into the holw to see if an HDD can catch a cold.

  15. Spawndon

    really?
    ok then i will get a straw and blow hard into the hole, and see what happens.

  16. Edmund

    I thought the hole was the equivalent of the tag you are not supposed to pull off of mattresses! Now I know better, however what’s up with the tag on mattresses?

  17. Showing my age

    Edmund, you are allowed to pull, cut or otherwise mangle that tag. In fact, the point is that you are, as the consumer, the only one allowed to pull it off, to ensure that the customer sees the legally mandated content and other information therein. Once they are in the customer’s hands, it is open season on tags. This also applies to tags other than just mattresses.

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