Drive (two partitions) "improperly ejected" - what to do?

Hi …

Not a good day for this. As I was working away, suddenly two “announcements” appeared saying that both partitions of an external drive (Macintosh HD-BU and Data Storage) had not ejected properly. This is not something I need today. Obviously, I’ll need to be ordering one or more new external drives, but if I can get this one back up and running before new ones are available, I’d like to do that. Disk Utility, of course, does not see it. Is this a candidate for Disk Warrior or must the disk be mounted before that can happen?

I need all the advice and suggestions I can get. These situations surely elevate my blood pressure , but the worst is that I can’t think straight.

Thanks much.

Disconnect and then re-connect the external drive. It should mount properly.

There is something in recent releases of macOS that does that, but apparently without damage.

It’s possibly the cable. If you have another cable that has appropriate connectors at both ends, try swapping it with the current cable.

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If it is a thunderbolt drive, I have been less than impressed with the design and find it very easy that an adjustment to an iMac monitor will jiggle the wires and result in a disconnect. Not sure why this style plug does that.

When you do get the drive to re-mount, I would open it in Disk Utility and run “First Aid” on it, at the very least.

Disk Warrior only works on HFS+ drives, but if this is one of those, I would definitely run DW on it, if only out of an abundance of caution.


Unfortunately, random ejecting seems to be a problem with all USB external drives. I’ve had to deal with it for many years and many different macOS versions.

I used to work around the problem by using FireWire drives, but that’s really not a viable option these days because it’s very hard to get new hard drive enclosures with FireWire ports and FW800 is significantly slower than USB3.

If you see this happen only occasionally (say, once every few weeks), just power-cycle the drive and move on. Maybe use Disk Utility to verify the drive afterward.

If it happens more often (e.g. daily or more often), then it probably means the drive itself is failing and you should get a replacement before it completely fails.

I began experiencing this on my shiny new iMac 2020 a few months ago, and spent several hundred dollars extra to unnecessarily buy new (software RAID) backup drives. The problem kept recurring. It finally went away when I gave up trying to get my Apple 30″ Cinema Display to work via USB-C to Mini-DisplayPort to DVI-D adaptors and replaced the Cinema Display with a second-hand Apple 27″ LED Cinema Display. A variety of glitches led me to diagnose a (probably firmware) error in the USB circuitry used in the adaptors (all from the same factory, despite different badges). Ditching the adaptors stopped all of the USB errors.
So although my problem is likely distinct from yours, I would suspect a USB fault somewhere, Can you try swapping out USB connections to isolate a possible source?

I have a similar periodic problem of disks being ejected improperly on a 2020 MBP. The hard drive and SSD drives are connected by thunderbolt through a CalDigit dock connected to my MBP through a Thunderbolt port.

Do all of you who see this issue frequently leave your drives plug in for many days at a time?

I have yet to encounter this problem on Macs despite using various generations and models, as well as using all kinds of different drives and enclosures. I have drives attached straight through USB, but also some through USB to a TB3 dock. One thing I do though, is I usually never leave a specific drive (or dock) plugged in for more than 16 hrs at a time. I’m wondering if the issue only shows up after longer connection periods.

My drives (16 totaling in excess of 60TB) are plugged in 24/7/365 and my iMac running Mojave is up 24/7/365 sans occasional reboots due to installs etc.

This issue is very rare in my environment, I did begin having it relatively recently on a 4TB drive used by CCC. The issue started unexpectedly, persisted for several weeks and disappeared after a recent Mojave security update.

The drive I see it on is my Time Machine volume, which is mounted 24x7 (attached to a Mac mini, which is the household server).

I find the drive dis-mounting about one itself every 2-3 weeks. My previous computer used a FireWire drive for this, which never dismounted itself (except when the drive inside the enclosure started getting flaky).

On my wife’s laptop, we see something similar, but the problem occurs far more often because the computer often goes to sleep with the drive attached. Again, switching to a FireWire drive prevented the problem.

Um, yes and no. The USB cable is plugged into a hub for weeks at a time, but the other end is connected to the drive only when I want to access it, which is about five times per week.

Even though I rarely see the problem, it does recur and I’m on my way to unplug and replug each USB cable at the hub now.

I was going to suggest trying to power cycle that USB hub once daily to see if the issue disappears. Not saying that’s a decent workaround, just trying to figure out what is actually going wrong.

That’s an interesting idea. I actually have two hubs, and the external drive (SSD) that usually plugs into the hub that is power-cycled almost daily (for other reasons) has never (as far as I recall) had an “improperly ejected” message.

On the other hand, again as far as I recall, every “improperly ejected” message has been about a disk with a spinning platter, regardless of which hub the device used.

This frequently happens to me. I have an OWC TB2 disk dock (2 slots), connected to my 2019 iMac with a TB3->2 adapter. One drive is a CCC clone, the other a TM drive. I have a rotating backup, so two sets of disks.

Sometimes both drives will go a full week without disconnecting. Other times, they’ll disconnect daily. Sometimes one drive will disconnect and not the other, though eventually the mounted drive will disconnect. The disk used doesn’t seem to matter (the disks are different models, HGST and Toshiba).

I’m still running Mojave, will be interesting to see if anything changes with Big Sur (once that hits .2).

Turning off ‘Put hard disks to sleep when possible’ in Energy Saver fixed this problem for me.

That’s already off…for a long time but I did go and check since Big Sur might have turned it on again…nope.

I can’t believe how fragile USB drives on MacOS seem to be. I was seeing constant (almost daily) disk ejections from my 2019 iMac running Catalina. This applied to both USB drives and TB3 drives hooked to the USB-C ports. As well as USB drives hooked to the USB-A ports directly (a powered hub seemed to mostly fix the USB-A connected drives, but even a hub did not resolve issues with the USB-C ports.

This is in contrast to my Mac mini (2018) running Mojave which never had a problem with any drive - including drives that would routine eject on the iMac.

In my case the fix was to apply the most recent Catalina security update which somehow resolved an issue that had been driving me nuts for nearly a year. (I had tried every workaround/fix I could find)

What bothers me the most is that there does not seem to be one underlying cause (or fix).