I want to get 2TB HDD in addition to 512GB SDD I have.

I want to be able to "turn off" that drive so that it stays off even after sleep cycles and everything... I'm worried because now when I have an external HDD and I eject it, it wakes up sometimes - for example just by launching Finder which accesses it... not sure, maybe it happens only after I wake computer form sleep, but still... I really don't want such behaviour in an internal HDD. It should stay "dead" until I resurrect it only when needed. Is this possible?

I don't know why is this information so hard to find - nobody reported it, just guesses and partial solutions on forums... So anyone with such setup - can you try?

  • An external HDD may solve the problem you're having, once you unmount it, you can then physically disconnect it. If you need another internal drive, what is the problem with keeping it mounted? – wrossmck Apr 21 '14 at 15:12
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    I would like to have storage internally... so I don't have to keep plugging in the external drive all the time. It's much more convenient esp. since I move around a lot. Also I have a Mac because I think I'm a power user... these kind of things should be possible and it's (I think) a common use case. – davidhq Apr 21 '14 at 16:32
  • I've only seen people have another drive internally who have it mounted all the time. Since it won't be your boot drive, it should be fine to keep it mounted internally (despite the power requirements, which are very low). – wrossmck Apr 25 '14 at 8:39
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    ok, will it still spin (slowly) if it goes to "sleep" after a minute? – davidhq Apr 25 '14 at 20:05
  • Unfortunately, I'm not in a position to say (or test) if it will still spin or not once in sleep mode. I would wager it's not the case, but that's probably a good candidate for another question here. Particularly since we like to keep questions/answers succinct. – wrossmck Apr 25 '14 at 23:42

I suggest to test and use: Disk Arbitrator.

This is a small application interfacing the MacOS X disk access interface. This application may be used in forensic investigation, to protect against unwanted connection of external disks, and to manage very straightforwardly any mounting and eject of internal or external disk (through the Show Disks Window menu entry).

I wouldn't speak in place of the author, but I can ascertain this tool is working on: Lion, Mountain Lion, Mavericks & Yosemite.

I haven't found any bug in this application, and I would be glad to give the same nul result with many application I have to survive with :(.

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    Confirmed working on Sierra 12.1 as well. – Zac B Nov 4 '16 at 12:47

It won't stay ejected. When you reboot it'll be reattached. You can, however, fix this. I had to tackle the same problem when my internal drive failed on my iMac. The key is to tell the OS, via /etc/fstab that you no longer want it to mount the drive.

To do this you'll need the UUID of the drive. You can get this from Disk Utility. With the UUID in hand you'll make an /etc/fastab entry by opening a terminal and typing:

> sudo vim /etc/fstab

And then putting the following in there:

# Internal iMac HD that's dead
UUID=1B39A092-75B2-357E-97FB-23C082975B80 none hfs ro,noauto

Replacing the UUID in the above line with the UUID of your specific hard drive.

Here is the specific block of text I kept in my /etc/fstab file until I replaced the drive: https://gist.github.com/ianchesal/7389200

That chunk references this question and answer: Prevent BootCamp partition from automatically mounting -- which is where I got this solution originally. It worked great to keep that bad drive out of the way until I could crack open the iMac and swap it out.

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Eject is only temporary, once restating the computer will read the disk again if it is still plugged in or you freshly plug it in.

So use the unmount in disk utility that is permanent till you mount it again.

I forgot, also disable the Spotlight search for that disk, so it wont spin any more.

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  • I know about the computer restart - don't care about that, I don't restart often. I just tried something with my external HDD now - clicked Unmount in Disk Utility... the drive was still spinning, clicked Eject Partition - it stopped spinning. Put computer to sleep, woke up, HDD started spinning!! That's exactly what I would not like with my internal HDD once unmounted. Is this possible to realize or simply the answer is NO - then I'll cancel my HDD order... I want my computer to act like it doesn't have spnning drive until I say it does (or I restart the computer) – davidhq Apr 21 '14 at 14:33

We develop an app called Mountain. The app provides a feature to spin down an ejected internal disk after waking up from sleep again. Enabling "Detach unmounted volumes on wake from sleep" in the advanced preferences should do the job.

enter image description here

You can run the current beta version without limitations for a limited time. You can find a link to the beta version here at the end of this article.

I would be glad to know if this works for you,


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