Yosemite ejects external drives

Dear gdo,

Yes, I'm running iTunes 12.4. I always install the latest updates for security reasons, as well as for improvements, so when they come, I install without too much question. I have no idea whether iTunes could have caused the problem, but I hope and trust that Apple will work it out soon. The ejection problem seems to be so widespread and across so many devices that trying to find the problem on our end is most likely not going to be the answer. I certainly am not a computer guru like the folks at Apple, so about all we can do is keep educating ourselves on what problems others are experiencing and how widespread the ejection scenario is. As I said, I haven't been bothered too much lately, since the latest batch of updates, but I've not used the problem driver very much, either. I did have a thought on that subject however. I wondered if having TWO external drives working at the same time might cause one of them to encounter problems, so I unplugged the one that was causing the problem and for a while only worked with ONE external drive at a time. I have two working right now, but the one that gave me the most trouble is not plugged in...and if I use that one, I think I will only have that particular drive plugged in...we'll see.

Your last thoughts are very interesting indeed. The ejection problem happens to me only when two external drives are connected. I had to copy a 500GB backup file from one drive to the other and it kept disconnecting. All in Thunderbolt, both connected directly to the computer, with Time Machine running in the background.

Since a couple of months now, I did not experience the problem anymore. But I did not use two drives at the same time as well.

Dear Sunset,

I mentioned before that it seems that the drives can't keep up to the speed required and just eject themselves. The more I stored on the problem drive, the more it ejected itself when called upon to perform. I have many photos on these drives, and when Adobe Bridge was doing its search was when the problem most often occurred. I could, however, transfer large files from the iMac's hard drive to the external drive without much problem, so it seems that sometimes the external drives just can't keep up with the speed required. One would question why the drive would eject itself, however, almost immediately after computer start-up in the morning and when it was not being called upon, but I suppose that all of the external drive's contents are indexing themselves for iMac's Spotlight search, so the drive is being called upon even though I am not using it directly. I really do think it's some sort of speed conflict between the USB 3 or Thunderbolt connections and the external drive, but, again, I am not up to the level of the computer gurus who tackle these questions, so I will have to leave it up to them to solve it. Because it is happening to so many different brands, I question whether trying to send in any drive under warranty would fix the problem.

Thanks for your views. I think as well, that the problem lies on Apple side and sending a drive to warranty will not solve the problem.

Hi Barbara

Again, many scenarios make troubleshooting difficult, but all these stories seem to point to Apple hardware or firmware.

To reply to your description, my troubles have always occurred in a 4-bay enclosure (OWC Elite Pro QX2, with Hitachi HDDs). While troubleshooting over the past year, I tried those exact same HDDs in separate enclosures, up to four daisy-chained, with NO issues. Note that others on this thread do have issues with individual standalone HDDs.

You might think that would point to the 4-bay enclosure, but I had it replaced twice (warranty), and each time it worked fine for an extended period of time. Until it didn't. That last time it started going crazy immediately after I updated to iOS 9.2 (via iTunes).

Since the last enclosure replacement (3 months), there have been no issues. But I'm still reluctant to update iTunes for now.

I'm fairly detached from everything: no Cloud, Apple Music, Sync or WiFi. No Time Machine or Spotlight.

I still think that there is a voltage mismatch between two sensitive ports – or port drivers – that causes the eject. I'm not even sure the HDD is actually ejecting, since it reappears. But that's a gamble we can't take.

If this thread is any indication, it appears that Apple has looked at it, cannot replicate the problem, and have closed the case.

Not good.

On the other hand, I've no problems for now.

nicwilson58 wrote:

One thing of note though, boot one of my Macs into Bootcamp and I ran windows 10 on it doing various things over a weekend and it not once got a disconnection, so its not power related, its not hardware related its OSx

Please FIX IT

Somewhat the same for me on my i7 iMac Retina with El Cap. Firstly, if I use my 3TB WD in a USB 3.0 dock it disconnects after a few minutes, sooner if copying a bunch of files. However, pop the same HDD into a similar USB 2.0 dock, using the same USB port in the iMac, and it copies ~30TB without a hiccup - just slower. I've tried 3 different USB 3.0 cables getting the same failure.

And then similar to nicwilson's experience, I can run Win 7 or Linux in Parallels, and using the same 3TB WD HDD, the same USB 3.0 dock/cable and same iMac USB port, and happily copy files for ages without a disconnect.

Six external drives were running without problems under Mavericks 10.9.5 on my early 2011 MacBook Pro. I just “upgraded” to El Capitan 10.11.5 and got the first disk ejection while Migration Assistant was pulling in files from the backup drive. After several attempts, I got all the files transferred but I wish I hadn’t bothered. Each time Carbon Copy Cloner runs, the target drive dismounts after five minutes. I’ll have to go back to Mavericks. It was bad enough but this problem is worse!

Note: NOTHING has been changed except the OS. Clearly the OS is at fault.

Dear All,

Just thought I'd report in. Since considering the fact that having TWO external drives working at once might be the problem, I unplugged the older Mac Book Studio that was giving me the most consistent ejection problem and am just working with my newer WD My Book for Mac. I have had no problems recently, although this newer drive had also ejected before while I had two drives plugged in. I have decided to work consistently with this newest drive being the only one plugged and working in until the problems are solved, but that may be a solution for someone else out there -- it seems to have worked for me, but one never knows!

I seem to have found one remedy, hopefully, by doing one of the suggestions/work-arounds here - MacIssues

I did this bit - 'try adding the drive to Spotlight’s Privacy list and ensuring it is listed in Time Machine’s exclusion list (available by clicking the Options button in the Time Machine system preferences)' - and my USB HDD hasn't disconnected since. I also took the precaution of disconnecting other unused USB devices, however running with just the USB HDD connected in the past hadn't resolved the problem prior to this Spotlight edit. I guess Spotlight becomes overworked filling its cache with what it's discovered on a recently connected HDD and (Spotlight/OSX?) decides to cut the connection.

While I won't be surprised if it reappears again at times, since the underlying problem no doubt remains, it does mean I now get more than a minute or two to transfer a bunch of files off my iMac.

Dear Wilburight,

This is good to know, and I'll give it a try if I have anymore trouble -- right now I'm good, but others may not be and will try your solution. Meanwhile, I'll keep hoping that Apple will come through. Your findings seem to be very plausible, because I've often thought that the drives just can't keep up, and if Spotlight is indexing everything and going between two drives, it may well be that a drive will just eject when it can't keep up with the indexing. Working with only one external drive at a time seems to have been my solution, but may not work for others...we'll see.

I did speak too soon. I spent ages yesterday trying to replicate my earlier successful multi-GB transfer and it failed this time despite unplugging everything from my iMac apart from the USB 3.0 HDD dock. I reset Spotlight's Privacy settings in case an external USB HDD was ignored on a subsequent boot, but still no luck.

Now the next day, and I've restarted my iMac and tried again. It worked ... for about 3 minutes 😐 The next attempt only transferred for 10 seconds. Since then I've tried other USB ports, and reformatted a HDD to FAT32, exFAT, NTFS (read/write OK on USB 2.0) and OSX. All started to transfer fine, then 10 - 60 seconds later, all failed. Then I went back to Spotlight's Privacy settings again and did the same as the day before, re-affirming the USB HDD was on the list, but this time my transfer worked ... for 5 minutes and several GB, till it failed once more.

Beats me how I had it transfer 30GB on that previous occasion, but I suspect it's back to USB 2.0 if I'm going to get this current transfer done. Or borrow my wife's laptop PC and use its USB 3.0 port 😟

Relying to myself again, but I've been enjoying several uninterrupted 40GB file transfers between external USB 3.0 HDDs connected to my iMac by doing them in a Parallels Windows 7 VM. To my simplistic reasoning, that suggests that these persistent USB 3.0 disconnections are an OSX problem and not hardware.

That's exactly what I also think. I have an external 4-bay RAID connected under usb 3.0 (jmicron JMS539B). Worked fine until it didn't. The first times I did a very large transfer from other connected drives (from FW800 to usb 3.0) and it worked fine. The Raid works and I can't work from it with no problem, but now, when I try to copy from it to another drive (I'm not even writing to it, I'm backing it up) to another drive (doesn't mind if it's a fw800, usb 2.0 drive) it dismount and remount immediately. If it's connected to a usb 2.0 port, that NEVER happen. Run AJA system test or Blackmagic Design speed test and most of the time it dismount and remount the drive. Did the same test via usb 2.0 and it didn't happen.

The question is: why is the drive ejecting itself? This is a usb 3.0 speed problem that doesn't happen under windows with the same drive.

I've been puzzling with this issue for a couple of months and slowly trying to identify what is stable and not (given these are my primary working / live drives in some cases I tread gently) - it seems to be the larger 3 1/2" drives with the main problem even though they are powered externally to the Mac (Late 2012 Mini with El Capitan and two internal SSDs). The smaller drives (2TB - 2.5 in) that are powered from the USB line seem to give zero issues to date.

Normal set up is to have two external drives plugged in at once but these have a power switch so they are 'off' most of the time. I use them for TM backups and general file copies / archive normally using Carbon Copy Cloner to duplicate files.

I also have a Time Capsule (WiFi connected) that has had no issues with both TM and file copies so far (July last year is the start of the TM backups). I have a LAN connected NAS (Synology DS414slim) that does not disconnect and I have moved TB of data fine over WiFi (not quick but solid).

Sleep mode is enabled on the Mac (an hour) and drive sleep is ticked

Note all of these have Spotlight privacy set on them so I know that does not help.

I have noticed that the WD drive does not always get mounted or show up in Disk Util / Finder first time around if both drives are connected at the same time (no matter if the WD is powered up before or after the Seagate) - fortunately I do not need to copy from one drive to another.

First question: I wonder is it the capacity of the drives - I have two 4+TB drives (one 4TB WD and one 5TB Seagate) and they have been problematic in two different housings (Probox and Ministack)?

Second question: Would two or more partitions on them cause the issue - I have two on both drives (one Time Machine and one for files).

Third question: Is it speed of transfer thats causing the issue with external drives? Not convinced as the WD drive was Firewire at one point and that had issues. I put that down to the WD drive though as I do not like them and had issues for years with them failing in Windows PCs.

Forth question: Is it machine type - mine is a mini but I've not tested the MacBook Air

Gut feel is its a combination of max drive size and interface speed - I think I will get a small (1-2TB) drive from HGST and fit it into the Ministack and test that under Firewire and USB...

I'm typically having these USB 3.0 drop-outs with a 3 partition 3TB WD HDD in a AC powered USB 3.0 dock. I have an 18 month old iMac i7 Retina running the latest El Cap. I also occasionally see mounting errors on an initial connection - second attempt is usually OK. My TimeMachine HDD (often in the same dock) is a 2TB Samsung and hasn't shown up any errors in 18 months.

I can't help thinking the size/brand is a factor towards its low tolerance for USB 3.0 faster transfer rates.