Big Sur Disconnecting My External HDD

OK, I have been doing some experiments and have not had a disconnection for a couple days. It appears (for me at least) as the trigger for the "DID NOT EJECT PROPERLY" event is when the Mac goes to sleep. I suspect it may be a combination of factors which I have not deciphered yet, including 1) Sleeping, 2) HHD, 3) TimeMachineBackup, and possibly marginal hardware.

By setting Energy Saver settings as follows and not manually entering sleep I have avoided the Disconnect for a couple days where it was reliably occurring at least once a day.

Can someone please try this and tell us if this works for you.

I am on an iMac where battery is not an issue so staying awake just wastes energy. This will have a more significant impact on Laptop users trying to conserve battery.

I have opened a Bug Report but it would be nice if Apple would at least acknowledge this is an issue that will be fixed. Apple?

As I pointed out earlier: I WAS plagued by this problem on two different HDDs (up to several times per minute!), a bus-powered and an externally-powered, and I verified that Sleep was not involved.

THEN I changed the USB cable (both drives had used the same USB Type-A cable that came with the first drive). I replaced it with a USB-C cable.

It has been three weeks and I have not had the problem At All. I leave my Mac Mini on 24/7.

You may have different circumstances, but this is mine.

Solved for me: I've had the same problem with a WD USB 3.0 drive on my wife's iMac for Time Machine backups (use multiple disks; this the only one that continuously dropped when the Mac woke up), thought it might be the USB hub, tried one with more power ... same thing, then, since I am using a bluetooth keyboard and mouse, was now able to plug directly into iMac... same thing. The problem drive was purchased already formatted for the Mac; noticed a post that there could be some software from WD that was causing it to hibernate and causing the problem ... reformatted the drive Mac OS Extended ... problem gone!

My brand new 27” IMac was consistently disconnecting both of my WD Ext HD’s. With the help of Apple’s engineers, it has finally been resolved. I thought it had something to do with Big Sur. Turns out it was my Trend Anti-virus. I had to remove all traces of Trend AV on my computer. It worked.

Do you use Trend Anti-virus, by some chance? After working with Apple's senior level support and having engineers go through my computer data, it came down to the Trend program. I had to remove all traces of Trend, with the help of support, and then the disconnects stopped. If you keep having the issue, I would suggest you reach out to Apple's senior level support, and ask them to send your computer data files to their engineers. If you have Trend, get their support services to help you remove ALL files and folders associated with Trend. Trust me, they're hidden in all sorts of places that you might not be able to find on your own.

I believe you are right and it is power related. The disconnect only happened for my HDD and not never my SSD. Once I disabled sleep it never happened again. I suspect Big Sur added some optimizations for the M1 Chips to minimize USB power usage and are treading close to the edge. Some unlucky Macs whose hardware is on the edge manufacturing tolerances are susceptible while for others never see the problem. Completely conjecture, but this started immediately after updating to Big Sur for me and many others. Too much of a coincidence to believe this is not the result of Bug Sur change.

So for 3 days now, I have had no issues with my external HDD disconnecting, what I have done is set my computer to never sleep. I set the slider for ‘Put monitor to sleep after’ to never, and it seems to have solved the problem. Of course now I have to manually turn my monitor on and off, which is less than convenient, but at least now I don’t have to worry about any possible data corruption...

I have some considerable progress -- Your mileage may vary, but:

As I noted earlier: I had swapped external USB 3-connected hard disks, and the problem remained: Initially all was reliable, but 'soon' (weeks) both disks (one USB-powered, one externally-powered) started suffering this problem -- as frequently as several times a minute. I'm running a late-model Mac Mini with Big Sur, fully updated, and NO sleep nor power-saving enabled, and the disks were only being used for Time Machine.

Desperate for some fix, I bought a new USB Type-C to Micro-B 3.1 Gen2 cable (the latter is the funky connector used on my external disks), and connected it to the very same 'failing' externally-powered disk.

Three days later and NO spontaneous disconnections! (so far...)

I don't know if the difference is that I'm using a USB-C port (instead of the USB -3 Type A port) on the Mac Mini, or if I had a questionable USB cable (I had changed neither when I swapped disks).

The above SEEM to implicate either a bad/questionable cable, or the USB-3 Type-A port on the Mac Mini. Frankly I sorta don't care, as it seems to be solid now(!)

Same Issue

Computer: MacBook Pro (16-inch 2019)

I've had similar issues and multiple hard drives disconnect several times. Files won't be viewable, the hard drive couldn't be ejected. Uploads and Downloads fail in mid-process. I can't tell you how frustrating it's been. Interestingly enough I used the same drives on my wife's 13-inch MacBook Pro wotjh Big Sure (no touch bar) and had zero issues. After multiple phone conversations with Apple and submitting my MacBook Pro to AppleCare late last year, the best they could do was wipe my mac and revert back to Catalina v10.15.7.

Since late December 2020, I've been on Catalina and I've had only to deal with a hard drive not ejecting once.

It's not ideal but apparently there is no fix for this yet. Looking forward to seeing this nightmare come to an end for all of us.

Update: Yesterday I was informed that the drive model I have has had some manufacturing issues, and a firmware patch was developed to remedy the issues. I find it odd that over the last 7 months, none of the drive support personnel mentioned anything about manufacturing issues.

I've requested that HGST/WD/G-Technology verify a drive that has the latest firmware and send it me. We'll see.

FYI, I really don't think it has anything to do with the OS, as I've been running Windows 10 Pro in Bootcamp for over a week, and the same issue persists. My other TB3 peripherals work fine in Windows.

I have had problems with disconnections since upgrading my 2016 MacBook Pro 15" with Touch Bar from Catalina to Big Sur 11.1 in January. At first it was only my 3 QNAP NAS drives that disconnected, the external USB drive I use for Time Machine did not disconnect. I have had QNAP NAS's for many years and never had such a problem with them before.

All 3 NAS's continually disconnected from this MacBook only after upgrading to Big Sur but never disconnect from my other Macs - a 2009 iMac running El Capitan, a 2012 MacBook Pro running Sierra and a 2014 Mac Mini running Mojave. The problem had to be Big Sur but I didn't know why.

This MacBook has 4 TB 3 (USB-C) ports therefore I needed a TB dock to connect other peripherals and bought an OWC TB 2 dock in 2016 later supplemented with an early model Hyper Drive 6-in-1 hub. The OWC dock gives me an ethernet port for access to my network including the 3 NAS's, an HDMI port to run a 2nd monitor and USB ports for the Time Machine external drive and spares for occasional drive connections. The Hyper Drive hub gives me an HDMI port for a 3rd monitor and a USB port for my DAC.

I lived with the disconnections from the 2 NAS's I used for backups, but got frustrated with the disconnections from the main NAS which is my main business file working drive. In my business I have collected literally millions of documents many of which I need to refer to everyday in order to write reports, papers and articles. Disconnections on this NAS are a real issue for me.

BS 11.1 caused disconnections from the NAS's but no obvious disconnection from the internet or the rest of my network. The upgrade to BS 11.2 made no discernible difference to the problem. The next upgrade to BS 11.3 seemed to make the problem slightly worse.

But BS 11.4 was a disaster. As soon as 11.4 was installed the MacBook crashed and re-started every few seconds to few minutes with a kernel panic. I eventually managed to stop it from crashing by switching from an ethernet connection to a wifi connection.

But the disconnections continued to occur every few minutes. I could be writing a report and try to save it every few minutes only to find the file I was writing to could no longer be found and I had to use Finder's Go To Folder menu to re-establish a connection for another few minutes.

Additionally, the Time Machine USB drive (via the OWC TB 2 dock) was continually disconnecting without being ejected and the USB DAC (via the Hyper Drive hub) was now continually disconnecting, this had not occurred before BS 11.4.

I seem to have solved the problem at last and am reporting my solution here. I have stopped the MacBook from ever going to sleep whether on battery or power adapter - I only ever use the power adapter, yet still needed to ensure never to put hard disks to sleep when on battery. The same with turning off the display, it is now set to never on both power adapter and battery. I do not understand why this setting is required for battery even when I am using the power adapter. After making these changes and seeing no more disconnections I switched the wifi off and re-started the ethernet connection with no further problems.

I have now been running for some 27 hours without a single disconnection of any type - it is a big relief.

From reading the posts above, it seems that others have been finding a similar solution though not everyone. Hopefully this post can help in some way. If I get another disconnection despite my "fix" I will report back.

Finally got it all to work out - at least so far so good. I reformatted the external HD and clicked "encrypt" box and created a password and it was able to do a full back up through time machine again.

Good luck everyone

I was having the same problem, with multiple external HDDs ejecting repeatedly (super frustrating as I know you know). As soon as Big Sur 11.1 became available, I updated to that and it seems to have solved the problem 🤞🏼 Good luck!

An additional observational datapoint, this occurs with me with the M1 mini and I found out how to reproduce (and work around). For me, this only happens when using Adobe Premiere CC using Rosetta 2 "intel emulation."

I've found that whenever the app writes to a thunderbolt drive (standard USB works fine) it will immediately disconnect and reconnect. My steps to repeat were simple: using adobe premiere CC if you "save" a snapshot of the current timeline frame (export as PNG for example) to the remote thunderbolt disk, it disconnects (never writes) then reconnects again (giving the warning notifications). Every. Single. Time.

When rendering, the minute adobe premiere writes to the 'cache' (a separate external thunderbolt disk) I get the notification again and again for each write operation.

I am not sure if this is a rosetta 2 thing or an adobe issue, but I'd imagine if you have adobe products open in the background, if they do write operations on that disk, you'll see a flurry of notifications.

Try preventing the Mini Mac from sleeping. See https://discussions.apple.com/thread/252083720?answerId=254371035022#254371035022 for the Energy Settings. Seems like am Apple bug to me given threads I have seen.