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How do you turn off/spin down an iMac's internal hard drive?

My iMac is about a year old and the internal hard drive makes an annoying high-pitched whine that's pretty normal for older drives.


No problem, I connected an external SSD via USB and boot off of that. It's nice.


The problem is, I can't figure out how to turn off/spin down the internal drive. Here are the things I've tried:


1) You'd think just dragging the drive to the trash can (in the Finder) and thus unmounting it would cause it to spin down. It doesn't.


2) You'd think that enabling "Put hard disks to sleep when possible" in System Preferences would eventually spin the drive down especially because it's unmounted and therefore must be idle, but it doesn't.


3) I did find one way to spin down the drive (after one minute, at least) using the following steps:

Use Disk Utility to mount the drive and unmount it again

Use this Terminal command: sudo pmset -a disksleep 1

Unfortunately I have to repeat these steps every time I boot the computer or wake it from sleep, which is a huge hassle.


Any help with this problem or just information about it is greatly appreciated! Ideally it seems like there must be a magical command line to run or file to edit such that the drive will spin down when unmounted. Crossing my fingers.

iMac, OS X Mountain Lion (10.8.2), 27", 2011

Posted on Oct 29, 2012 4:38 AM

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27 replies

Oct 29, 2012 11:07 AM in response to rkaufmann87

The noise mostly bothers me when I'm using the computer, which I have to do most of the day for work, so putting it to sleep is not a viable option.


As for getting it serviced, I'm sure the iMac is operating as designed. It's normal for hard drives to make this sort of noise after they're a year or two old. I can't imagine Apple would replace the drive. I just seem to be particularly sensitive to these sorts of high frequency noises.

Oct 29, 2012 3:45 PM in response to motrek

If the HD is making a very clear high pitch whine, this is an indication that the drive is, in fact, failing!

Spinning down or sleeping the drive is the least of your issues.

You need to backup/clone your internal drive to either disc or an external drive and bring your iMac in for a hard drive replacement before any catastrophic failure are data loss occurs.

To clone data from one drive to another, you need to download and install cloning software.

Use either Carbon Copy Cloner or Super Duper.

Oct 29, 2012 3:51 PM in response to motrek

The sound is not normal, I have a three year old iMac and the hard drive males very little noise.

This drive is, indeed failing and you are avoiding the inevitable outcome!

You need to have this drive replaced!

With spinning platter hard drives their failure isn't a matter of if it fails, but when.

Backup/archive all your data onto an external drive and bring your iMac in for servicing/hard drive replacement!

Oct 29, 2012 4:12 PM in response to MichelPM

Thanks for trying to help but as I mentioned in my original post, I'm not even using the internal drive anymore (which is why I would like to turn it off) so data loss etc. is not an issue.


As for the sound indicating impending failure, not really. I have been using computers for 30 years and know how hard drives sound. This one sounds pretty normal. It's just annoying me. I guess I have sensitive ears.

Oct 29, 2012 9:40 PM in response to RRFS

Sorry, I guess I wasnt clear with my first post. I *can* get the drive to spin down by remounting it, re-unmounting it, and then running a pmset command in the terminal. I made a script to do this actually, which I unfortunately have to run every time the machine boots or wakes from sleep. I was hoping for a solution that's less of a headache.

How do you turn off/spin down an iMac's internal hard drive?

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