Big Sur - external discs not mounting

Solved ... for me at least ....Disk Utility -> First Aid

I had a very similar issue with my brand new Macbook Air M1 with BigSur 11.4

I have two Seagate 8TB drives, both formatted as eXFAT, which worked perfectly on my 2015 Macbook Pro Retina and an aged Dell M6800 running Windows 10.

No matter which drive, no matter how connected (Anker 6-in-1 PowerExpand usb-c hub. or another dongle usb-c to usb-3), I would ... a) not see the drive in Finder b) In Disk Utility the drive would be seen as not mounted, and would not mount manually c) powering up with the drive made no difference

Following an Apple Tip in this thread, I then ran First Aid on the drive using Disk Utility, but... FIRST: attempt a Disk Utility -> Mount, wait a while and close the error message that says can't mount .... important step. Then Run First Aid ...... a) select the show details tick box so you can see what's going on then proceed b) Accept any "can't mount" or "unmount" messages if they appear c) after very few minutes the drive was "repaired", mounted, visible in Finder, and all files & folders seemed intact. d) continued to work when drive disconnected & reconnected Most importantly, after the "repair" the drive still worked perfectly on my old Macbook & PC

I'll check out that the drive works with the other dongles and also do the same on my other 8TB drive.

I've just done that with the same results.

I have the same problem continuously ever since I upgraded to big Sur. I am currently on Version 11.4. I have tried everything including running First Aid on all my external drives (I have 3 one of them is an SSD), but nothing helps. It is so annoying with in the middle of my work, two drives drop off! These days it happens 3 or 4 times a day!

SOme one suggested that I take Energy Saver off 'Default' for a little while it seemed to work now back to the same annoying Big Sur performance!

I have ALSO been having Drive and disk issues. This new bigSur MacOS is not as great as previous builds. Some things are nice and cool about it, others are absolutely terrible, like the finder window and toolbar space.... But back to the drives.... Mac OS Big Sur will trip on my external ExFat drives most notably after they are mounted on my windows 10 pc. I could also tie the issue to windows except that my older macbook running high sierra does not present those issues. Can you guys Downgrade/upgrade diskutil, and disk utility to that of older versions of Mac OS when First Aid actually fixed something, or gave us more controls to fix drives, permissions and etc?

I had the same problem on Mac OS Big Sur. Western Digital My Passport for Mac 5TB formatted exFAT. After 6 hours I came back and it had magically mounted. Eject, reconnect, mount OK in seconds.

I agree 100%. What is wrong with this company? They freely make changes that affects our data and hardware and then ignore us, the customers, with all the problems their changes create. And it's not; like they don't have the money to support their customers.

Apple killed its desktop unit a few years ago. Alas. latest OS's show the loss.

Reboot your mac. I had the same issue. Reboot helped me.

Hi all,

I have the same issue, where all my external drives stopped mounting after I upgrade to Big Sur. The problem is that they do not even show up in the Disk Utility app. It really upsets me since it is nearly 30 TB worth of data! I have tried all things posted here, but none worked.

I have two G Tech drives a Studio R and Studio XL both of which have run fine for years they are great and stable as and run on an older I Mac and I Mac Pro but friends have and still run fine on my 2015 Mac Book. I just proudly brought the new I Mac (brought last week, took seven weeks to get) spec'ed with more ram to then run Da Vinci Resolve 17 on and the two drives don't mount -- I am told they won't as the M1 chip is too modern and its not a hardware fault of the Mac but my drives -- I have spent about 8k on these drives and used them for some time in my work as an editor they are great drives and I am gutted that a brand new I Mac and now my wives new Mac book Air also M1 (brought today)won't see these drive. Strange thing is a 2014 G Tech Studio drive (6 TB) works fine so how come these two don't?????? Its thousands of dollars wasted when you think you are buying the best out. I don't know what to do as i need these drives for work and the content on them for work and they are great drives but i cant see them. NO where does it say from Apple that drives won't work with an M1 Mac not anywhere and its gutting to have invested in two you devices from the the I mac and Air and if I could return all my products I just about would as this is thousands of dollars of equipment that really doesn't do the job. Apple support say its not their fault that other companies don't keep up with them Does anyone have any ideas on this or any drivers from G tech???

This solution worked for me, after searching and trying all possible solutions on multiple forums. Some context: Running MacOS Big Sur 11.6, Disk utility first aid said "seems to be ok", fsck_exfat returned "seems to be ok", disk was showing up on Disk utility but could not be mounted.

Run "sudo /sbin/mount_exfat /dev/disk2s2 /Volumes/External-HDD/" on the terminal. Enter account password when prompted. My disk was formatted as exfat (use mount_<your disk format type>) and diskutil list showed the disk identifier as disk2s2. You have to first mkdir /Volumes/External-HDD/. Hope this helps.

Hey guys. I use 4 Seagate drives (8 TB Sata Enterprise v5). They aren't raids but are each a different drive that I use - Drive 1, Backup to Drive 1, Drive 2, Backup to Drive 2.

I inserted the backup drives in Orico's 2 bay hdd docking station (model: 6629US3) a week back in my MacBook Pro 16' 2020 that I had updated to Big Sur 2 weeks back. The hard drives Back up 1 & Back up 2 didn't show connectivity. I assumed it's the docking station’s error, I kept the drives back on a table to resolve issue later. 

The only change in anything is I upgraded to Big Sur from Catalina, rest is all as it was. 

2 days ago, I switched On my Main drive 1 & Main drive 2 (not raid), which are always connected but they showed no response. 

• The hard drives is showing as disk2s2 and disks2s3 on the left panel in Disk Utility.

• I tried mounting it, no response. 

• I tried mounting it through terminal command, didn’t work. (Could not mount ‘disk2s2’ .com.apple.Diskmanagement.dis enter error -119930868)

• I tried repairing it through First Aid, error. (First Aid process has failed. If possible, back up the data on this volume, etc)

• I then called on a technician in the city, a hardware expert, he claims that it may be the OS of the drive that's corrupt and needs reinstallation for which he asked me to write to Seagate. (The only explanation I think)

• HDD Docking station is working fine on other drives. 

• I have 2 HDD Docking stations. Both are working fine. 

• I have tried to switch USB cables, electric cables on the docking stations.

• I have tried different power supplies.

• I have tried the drives on Big Sur, Catalina and Sierra. No luck.

• I have tried it on Intel MacBook Pro 16' 2020 (BigSur), MacBook Pro 2015, MacBook Pro 2015 late, MacBook Air 2012 (Catalina), MacBook Pro 2011 (Sierra).

• The drives have been in the studio and nobody handles them but me.

• Drives haven't been physically damaged or repaired or any of that.

• Mostly AC is On in the studio.

• When I connect the drives, the drives switch on and there’s regular movement inside it seems. They’re heating up the usual way, the inside disc seems to roll regularly.

The drives have my career long data in them and I think I did everything right in the textbook and made backups. I have to recover them - there’s no way I can quit on them or I can erase them. 

How can 4 drives stop working like that. It’s not like the data has any corporate espionage. I’m a Producer. 

Either it’s some weird issue with Seagate or Big Sur or inter dimensional beings are messing up with me. 

Help, help, help.

Same problem here. Please fix.

Check your anti-virus to see if you have a setting to not allow external media. I went through all of the steps, typing in the Terminal line, running Disk Utility First Aid, trying to make the disk mount... Nothing worked. Finally made an appointment with Apple Care, the technician did an diagnostic, and they figured out it was the virus protection they sold me (ESET) that was blocking it. A simple checkbox. Argh! But fixed now.

Ok people, I spent 4 hours researching and trying all the solutions out there and finally found a fix that worked for me and wasn't mentioned in any of the answers submitted.
First of all, my machine is a mac mini 2018, 1TB ssd, 64GB of ram, i7 processor. Latest Big Sur MacOS version.

You will need an additional Window PC at hand.

What I did: 1- Installed APFS for Windows app from Paragon ltd on my PC. 2- Connected my external SSD and mounted it: which makes it now able to be read from and written to from my PC 3- Just explored the content through my window explorer browser: Opened a couple of folders, 2 or 3 levels down. 4- Unmounted it(I think this is quite an important step not to be skipped as Windows usually allows us to do that without issue but I suspect that the unmounting process somehow participate restoring the drive registry to a format that Big Sur will now be able to detect) 5- Connect the drive to the mac: It should now be detected and work as usual.

Hopefully this will save time and a few tears to some people. Nothing else worked for me.

Best

JG

Thanks  Billinski, your method worked for me too.