Big Sur Disconnecting My External HDD

I was able to stop the disconnects by preventing my computer from sleeping.

Since making these adjustments mine does not disconnect. However, since it is happening every 5 mins you may be experiencing a much more severe case. I suspect it is a power related thing.

Open a bug report to Apple. The more duplicate bugs they get the higher priority it will be.

I thought a fix would be imminent because of the impact.

It appears to be Big Sur. it is happening on all different Macs and different HDD drives since Big Sur.

It is a huge problems for those affected.

Sure would be nice if Apple Support would at least tell us Apple acknowledges this is a problem.

After having Apple engineers look at my operating system, for reasons of my new IMac disconnecting from my external drives, it came down to my antivirus being the cause. I was skeptical, but I followed their suggestions (with the help of a high level Apple support person) and removed ALL traces - hidden files and folders- of the antivirus program (which was Trend AV). It fixed the problem. That was three months ago. So, don’t hesitate to talk to the higher up tech support folks. It may be something similar and something you might never find on your own.

I have started to have this problem after having updated my MacBook 12" Intel to Big Sur. When I have tried to do my usual backup with SuperDuper, my external SSD started to disconnect. I normally connect it to a iTeknic USB hub and it was perfectly functional during the last backup before the update. SO clearly the problem is with Big Sur. It seems that BS does not like my hub, because I have plugged the SSD directly on the (only) USB-C connector on my Macbook using a USB-C-A adapter and everything worked like a charm. FYI: my hub is powered because I connect my MB's power brick on the USB-C connector on the hub and the hub powers my MB (since the MB has only one USB connector).

The direct connection worked for the backup with a full battery but it cannot work for Timemachine, since I need to connect my MB to power during the day, and cannot let the SSD occupy the USB connection on the MB.

I hear that some hubs do work with BS, but no idea yet why and which ones....

Funny enough, if I connect the SSD on the legacy USB 2 port on my hub (I have one USB2 and 2 USB3 ports), the connection seems more stable, but pretty slow of course :-(

I was able to fix this same problem (drive disconnecting after a few minutes or hours when connected to a USB port) by connecting the external hard drive to the Mac through one of the USB-C ports. I had to buy a USB-3 type B to USB-C cable to fix this issue.

Mine was being caused by my Trend anti-virus. Every shred of its existence had to be removed before my externals quit disconnecting. Weird but it worked. Apple engineers helped me solve it.

I had a similar problem with such hard drive but not only with Big Sur installed. I wanted to use the hard drive on a different computer, and it also ejected improperly sometimes with me doing nothing. What I did in the end on an older computer was to erase the hard drive and reformat as Mac os Journaled, GUID partition map. Then I ran into the problem that the disc was occasionally unmounted, when I connected and somehow erasing again failed. So I went to disk utility again and selected partition and then selected Mac os Journaled again. The disk was erased, and now it seems stable and working, although I am using it for a different computer with Catalina.

If you can you may want to reformat your disk again but may be somebody has a different suggestion.

Mine, after help from Apple's engineers, was my Trend Anti-Virus program. I had to remove ALL traces of it before the disconnects stopped. Senior level support guided me through the steps and search for all folders related to Trend. They were in remote places that only a senior tech person could have helped me find. Once they were gone, no more disconnects. I was expecting it to be Big Sur related. Guess it wasn't.

Mac mini 2020, Big Sur 11.2.3, external drive Samsung SSD 860 EVO 2TB 2.5 Inch SATA III Internal SSD installed in an AGPTEK USB Hub. I too had the constant disk-disconnected message after the Mini awakens from sleep (and usually the drive still appeared on the desktop and files on it were accessible). Tried Apple Care. Didn't help. Tried reinstalling system. Didn't help. However this did help. The cable from the hub to the Mac mini went into the mini's Thunderbolt port. I switched it to the Mini's USB-A port (used an adaptor). Now the Samsung disk doesn't disconnect after sleep - this after a few days of working this way. Not ideal, but it worked for me.

A month on - just to add that this set up is still working. Should also mention that, based on the suggestion of others on here, I have connected the external drives via a powered StarTech USB 3.0 hub. I haven't had a problem since - yet the issue with the one (older) Samsung drive/StarTech enclosure combination has not been resolved. This remains invisible to the mac.

If you haven't already, and the drives are bus powered, try connecting to a powered source other than your Mac, like a powered dock...

I am seeing this too. I have an USB connected hard drive which spontaneously disconnects ever few hours. I stopped Time Machine and still happening. I reformatted and created the partitions to all be APFS, still happening. Move the drive to an old High Sierra iMac and stays connected. Isolated to Big Sur spinning drive. No trouble with SSD drive. Wondering if I should not be using APFS on spinning drive.

History: The G-Drive Mobile TB3 SSD has been connected to my 2018 Mac mini since I bought it in June 2019. The drive worked great with Catalina. I upgraded to Big Sur in November of 2020. The drive started randomly disconnecting.

The drive was still under warranty, so I contacted support, they sent me a refurbished drive with a bad TB3 connection (port). I had to hold it a specific angle to get it to connect, and it also randomly disconnected while I was holding it. They sent a second refurbished unit. The behavior was the same. They sent me a third drive, but this one was brand new still in the sealed packaging. Same behavior...

I contacted Apple. They had me do the normal things that I had done multiple times, reset NVRAM, SMC, PRAM, enery saving settings, etc... No change.

Next they had me boot into safe mode and connect the drive. It connected and stayed connected. I rebooted into normal and it stayed connected. The tech stayed on the phone with me for about another 20 minutes. 30 miniutes after the call ended, it started to randomly disconnect again. It started to do it every few minutes, then it started about every 15-30 seconds...

Mac mini has 4 TB3 ports, 2 ports per BUS. I have an eGPU (Radeon Vega 64) connected to 1 TB3 port (it made it through the upgrade to Big Sur)

Caldigit TB3 Plus connect to the 3rd port (second BUS). It has multiple External connections (USB 3.0 type A drive bay with 4-6TB drives, USB-C Sandisk 500GB SSD, USB-C Sandisk 1TB SSD, all made it through the upgrade).

I've plugged the Sandisk USB-C 1TB SSD into each TB3 BUS, it works perfectly.

I've done the same with the G-Drive, but it behaves the same no matter what port it's connected to, that includes the TB3 port on the TB3 dock.

Appearently the Big Sur upgrade altered the TB3 configuration on the Macmini to the point this particular G-Drive Mobile SSD will NOT stay connected.

The G-Drive Mobile SSD is the only piece of my hardware that didn't survive the Big Sur upgrade. I would roll back to Catalina, but Big Sur allows me to boot straight to my eGPU. In Catalina, I had to boot to the local GPU, and switch to the eGPU after boot up.

Note: The G-Drive utility is not compatible with this version of macOS...

I'm going to contact Apple again.

I've had problems when backing up to an external drive in the past and I always run caffeinate to stop my MacBook going to sleep whilst running a backup (rsync).

I found opening the Terminal and running caffeinate solved my problem. Not an ideal solution I know. Maybe it'll work in this case.

Here's a thought. Earlier (before Big Sur), there were multiple similar issues reported. It appears, power was the main issue. As you know, the 2018 Mac Mini has 4 TB3 ports, but only 2 TB3 buses, so ports 1 &2 share a bus, and ports 3&4 share the other bus. My research has been limited to bus powered TB3 SSD's. I read an article in "Mac Performance Guide" mentioning this very issue. It is quite possible that using the dock with it's own power source is why it solved dschommers (above) connectivity issue.

It makes sense, lack of "enough" power causing intermittent disconnects. It also may be why the G-Drive shows up in the "Finder" and "Disk Utility" as a "SanDisk Extreme Pro"; however, it shows up in the System Information as G-Drive Mobile Pro SSD (see attached images below)...

So, when I connected to my Caldigit TS3 dock, why did it continue to disconnect, albeit much less frequently, but still the behavior persisted?

It was connected to my Caldigit dock from day 1. It was my home drive, so it was connected during the upgrade to Big Sur. I didn't add any hardware (Thunderbay was not added until this March-months after the issue started), and if it wasn't caused by the upgrade, then what?

It appears after the upgrade, the dock's power output was no longer sufficient to power the SSD properly...

Caldigit TS3 power specs:

AC Input : 100V-240V ~50Hz/60Hz

DC Output: 20V/9.0A, 180W

OWC Thunderbay 4 power specs (there are 2 versions of the Thunderbay 4 - TB3 and TB2 power for both is the same):

• AC input: 100 ~ 240V, 50-60Hz
• DC output: 12V, 16.7A

2018 Mac Mini power specs:

• Line voltage: 100–240V AC
• Frequency: 50Hz to 60Hz, single phase
• Maximum continuous power: 150W

Actual G-Drive Mobile Pro 1TB TB3 connection scenarios:

Mac Mini (direct connect): Constantly disconnects (15-20 times per hour)

Caldigt TS3 (connected to Tb3 port): Disconnects (1 per hour)

Thunderbay 4 (connected to upstream TB3 port): So far it hasn't disconnected.

Sys info today shows:

TB Bus 0: eGFX Breakaway Box

TB Bus 1: TS3 Plus

ThunderBay 43

G-Drive mobile Pro SSD

Sys info before the upgrade was the same but the G-Drive was under the TS3 plus.

Update (hopefully my last): WD/HGST sent me my 5 G-Drive replacement. It was brand new, still in the sealed retail package (not that it matters).

Those that have been following this tread for the last 4-6 months know all of the "trials and tribulations" that have been experienced by many of us when it comes to external drives and Macs, in my case specifically the 2018 Mac Mini.

My TB3 G-Drive Mobile Pro 1tb SSD disconnect issues began in Oct/Nov 2020 after updating to Big Sur. It worked perfectly in Catalina. After 3 or 4 months of troubleshooting, tech calls, replaced drives, and Apple Engineering combing through my Mac Mini, I decided to restore the Mac back to my last good Catalina build. That didn't work either. The issue was the same when I was running Win10 via Bootcamp.

Latest info: 3 days ago I received the 5th replacement drive. I decided to disconnect everything and put back together as close to the working Catalina configuration as possible.

The only thing I read throughout this entire debacle that is consistent is related to power issues. Originally my SSD was connected to my Caldigit TS3 (Thunderbolt 3 dock), and it worked perfectly. I was thinking the disconnect issues were caused by upgrading to Big Sur because that's when the issue first manifested, and while I believe that had something to do with it, I now believe the root cause was "POWER". No matter what TB3 port (including the daisy chain port on the TB3 drive bay and the TB3 port on the Caldigit dock, both are powered), it would still disconnect. The only difference was the time between connect-disconnect. It definitely varied depending on where I connected it.

I reconnected each device prior to power up. I move 1 connection (USB 3.0 type A-connected to multi port USB-A dock and a Startech USB-C SD card reader) from the Caldigit dock to on of the USB-A ports on the Mac Mini. I connected the G-Drive Mobile Pro SSD to the TB3 port on the Caldigit dock. The Caldigit TS3 is connected to the same TB3 bus as the TB3 drive bay. It's been 3 days and not a single disconnect.

I cannot figure out why the Mac Mini sees the SSD as a Sandisk Extreme Pro instead of G-Drive Mobile Pro, and neither could Apple engineering or the G-Drive team. When I initially bought the drive the Mac Mini saw it as a G-Drive Mobile Pro (icons and all), somewhere along this turbulent journey that changed, so there is still something going on. Hopefully it is separate from the disconnect issue...