External hard drive ejects on sleep

I recently upgraded to Mountain Lion and noticed every time I leave my iMac and it goes to sleep, the external hard drives eject. I get the pop-up stating they were improperly ejected. Anyone know how to stop this? Wasn't having any problems in Lion.

iMac, OS X Mountain Lion

Posted on Aug 3, 2012 6:21 PM

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450 replies

Oct 10, 2013 8:56 AM in response to BrooklynAL

ONE MORE data point!


My external drives are also ejecting after sleep.


I have 10.8.5 with the supplemental update already installed. I am experiencing the problem on the following hardware. ALL of these hard drives have ejected on their own.


2013 Macbook Air 13" stock config.

Seagate 3TB USB 3.0 hard drive, tried different cables and different ports.

Lacie little big disk 2TB thunderbolt

Buffalo Ministation thunderbolt in either thunderbolt or USB mode.

Oct 16, 2013 6:20 AM in response to iamapple

Still happening to me too. This is very frustrating. I also have applied the 10.8.5 supplemental update (and the original 10.8.5 btw). My WD My Book for Mac 2 TB, USB 3.0 drive disconnects all the time, thus preventing Time Machine backups. Kinda defeats the purpose of using Time Machine! Come on Apple, this can't be a hard bug to fix, can it?

Oct 16, 2013 8:07 AM in response to ad5901

I thought the same thing. Went about a week with no problems, and then had a USB 2 dock disconnect overnight. USB 2 (dual bay eSata and USB 2 thermaltake dock) and TB (Pegasus R4) had been working fine for months before 10.8.5. It was only USB 3 external drives and docks (StarTech USB 3 dock) that I struggled with. My problems with USB 2 started immediately after the 10.8.5 update. The supplemental update has made it better, but with 1 disconnect it hasn't been perfect.


I don't like how USB 3 drives ignore the "put hard disks to sleep when possible" system preference.

Oct 29, 2013 3:44 PM in response to iamapple

I now have a 2013 27" iMac with Two 1TB drives on uSB 2.0 and 1 2TB drive on USB 3.0 and none have the problem I had on my older 2008 iMac. I am using Mavericks now. I also have a 2008 iMac with Mavricks and a USB 2.0 1 TB drive and it doesn't disconect. I have a Mac Mini with a 1TB drive on USB 2.0 with Mavricks and no problems at all. I have my drives plugged into the computer directly and other devices into hubs.

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External hard drive ejects on sleep

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