My 10 T hard drive had been attached to my old iMac and backed up by Backblaze. I moved it to my 2020 iMac several weeks ago and began Backblaze backup here. It is backing up 3 or 4 T of pics and videos. Initial backup still in progress.
I bumped the cord yesterday, improperly ejecting the disk, and now it won’t mount. I have requested a usb restore from Backblaze which will likely be incomplete. I have also contacted support to see if the backup from the old machine is still with them, since it’s been over the 30 day mark.
Is there anything more I can do to recover my data?
Is the actual drive corrupt or just the data? Can I eventually reformat and reuse the drive?
Thanks,
Maripat
If you open Disk Utility, do you see any sign of that drive?
Most likely the drive itself is not damaged, and it may be possible to recover most of the data using tools like TechTool or DiskWarrior, or, if you’re really lucky, First Aid in Disk Utility (props to @MaxxHouseMaid).
Thanks for the disk recovery recommendations. The drive was grayed out in DU and clicking the Mount button did nothing. I inadvertently left it plugged in to the old computer over night and when I got in this morning it had mounted. What a happy surprise. So one lessen I’ve learned is that the data is different from the drive mounting, I guess. And that is a different thing than the drive health itself? All my files seem to be intact. Backups and hard drives have always been a bit confusing to me.
One more question, if I may, I have several old hard drives that I now believe to be still good. When I reformat them should I choose Mac OS Extended (Journaled)?
What OS are you using, and what do you intend to use the drives for?
My 2011 Computer is on Yosemite. My 2020 is on Big Sur.
They’d be a back up of sorts, possibly a Carbon Copy Cloner bootable backup on either machine. The 10T is for the pics and videos I need for my business.
And then there’s thousands of personal pics/videos as well.
I’m slowly manually transferring stuff from the 2011 to the 2020 machine. Since the 2011 is my first Mac, I didn’t have a file organizing system and there is digital stuff all over the place. I’m more intentional about the 2020. I’d imagine the hard drives will help with this transfer as well.
ASAP do a full backup of the 2011 drive to a separate external HD and/or a sufficiently large USB stick. Put a big red sticker on that hard drive or USB stick that says READ ONLY. Should you inadvertently destroy something on the 2011 machine, you are not dead in the water.
Also get a CD/DVD drive and burn the contents. Yes. Old school. But redundant and reliable.
At this point, you can safely wipe the 2011 and do a clean OS install. Set it up as you want/need. You will feel a sense of achievement when you do not have to wait to transfer everything from the 2011 to start using it because you still have to sort out the file system that you never had.
The USB C bus on a 2020 machine is fast but not solid state fast. If this matters for your work, pull things off the external drive / USB stick in chunks as you need.
Finally, run hardware diagnostic checks on the old hard drives before you put them into use. I can’t say that Disk Utility will do it all, but it provides a good starting point.
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JJW
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A perfectly healthy drive can refuse to mount if the formatting of the drive becomes corrupted, which is likely what happened when the cable was inadvertently disconnected. Since it’s a 10T drive I’m assuming it’s not that old so the disk itself is probably fine. It wouldn’t hurt to run First Aid on it.
Personally I would make two HDD copies rather than burn CD’s or DVD’s. Other than that I agree with @DrJJWMac.
You should assess the age of your “old” disks against the risk of possible data loss. HDD’s are pretty cheap these days.
As for how to format those disks, I think it’s fine to format them Mac OS Extended (Journaled), also known as HFS+. Big Sur or CCC will tell you if they want APFS instead (actually, Big Sur may just reformat them automatically, depending on how you’re using the disk).
Thanks for taking the time to respond. Can I get clarification on a couple of things?
- How do I asses the age of my old disks?
- Am I using software to create the full backup of my 2011 machine?
- After I safely wipe the 2011, what OS should I install and how?
You guys have given me much information and I truly appreciate it.
Maripat
I like playing the CD called TEACHING FOLDER BACKUP while I’m on a road trip in my 1990 Honda. You just don’t get the same quality sound from an HDD. But we are devolving into an 8-track tape versus cassette discussion here. 
- Look on the disk. It may have a date stamp somewhere. If not, you may need to do some detective work, perhaps at the manufacture’s site. Here is the site for Seagate warranty checks.
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You could use any software that will make a reliable backup. Indeed, you might even create a bootable backup with the entire image of the 2011 machine. The danger when you simply drag+drop files is that you can forget about “hidden” files in your Library folder.
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You can install whatever OS you want as long as you have access to the installation tools. This might be a starting point.
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JJW
You guys rock! Thanks for my new weekend projects 
I have had some weird behaviour with my 2020 M1 MacBook Pro when it comes to stuff plugged into it. That includes hard drives. One day recently I noticed both of the hard drives plugged into my OWC USB-C Dock were not mounted in Finder. So I went to Disk Utility, where oddness greeted me.
The Samsung T5 SSD was simply not visible. I plugged it directly into the MBP and it was still not visible. The WD My Passport HDD was showing in Disk Utility, but in a very weird way. The drive itself showed normally. The APFS container (it is used as a Time Machine drive) was greyed out and flashing randomly and very fast, like a cable wasn’t seated properly. I decided to shut down the MBP, which then sent me into a boot nightmare and when I eventually got out of that, both drives were perfectly fine.
I’ve also had frustrating problems with my LG monitor where the MBP will detect it, remove the menu bar from the internal display, along with the windows on it, but fail to display anything other than black on the LG.
In short, don’t believe an M1 MacBook Pro when it comes to anything plugged into it.
I’ve noted in a review somewhere (here and Amazon prime) that my LG27 UL 4k will only run stably and with its full suite of options when it is connected to my MBP 16in via a robust USB-C to HDMI adaptor. The LG was unstable or not fully-featured in any other connection option. If you are connecting to it through the dock or even straight through the USB-C, this may be the mistake. The dock might scramble something or the USB-C on the LG is not standard enough for the output from the MBP (or M1).
I use this adaptor …
https://www.amazon.com/Anker-Aluminum-Pixelbook-Compatible-Thunderbolt/dp/B07THJGZ9Z/
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JJW
Mine is a 27 UK so possibly an earlier version of the UL?
I should note that it had a very similar problem when connected to my 2018 Mac mini, where it was connected using a USB-C to DisplayPort cable. I now use that same cable from the dock.
One interesting aspect of the problems is the display has a ridiculous “no signal” timeout of around 10 seconds. So when my Mac mini would spontaneously reboot itself (thanks Catalina!) the time spent in the boot with no monitor signal would see the display shut down and then the Mac would be unable to see it and the fun would begin with multiple reboots until it apparently randomly decided to work again.
Inevitably, the MacBook Pro gets connected and disconnected far more often so the problem is far more prevalent, but most of the time I plug in the dock cable to the MBP and the LG screen wakes up and everything works! Just one time in 10 when it doesn’t it takes the same multiple reboot and pray approach to get it back and, I’ve noted lately, it often comes back with a massive purple colour cast! I’ve found that can be fixed by turning the monitor off and on again. At the right speed.
I’m fairly convinced now that the monitor is the root cause. I’m hoping real hard that “cheaper Apple monitor” rumour is true. If it’s a 5K iMac panel in an Apple enclosure then I will find the money! I loved that iMac screen.
Yes. I read somewhere that the UL is a noticeable improvement in stability. Also, I read somewhere that HDMI is the only port that supports the full set of 4k options.
In summary, I again would test every option on cable + adapter, especially USB-C to HDMI, before I boot out the monitor as the problem.
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JJW
I wouldn’t keep any disk that I had the slightest doubt about. The risk/reward ratio is too unfavorable, and HDD’s are cheap now.
I’d use Carbon Copy Cloner or SuperDuper.
What @DrJJWMac said.
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Somewhere I read, and I don’t know if it was the monitor or the Mac, that HDMI would do 4K at 30Hz and DisplayPort 4K at 60Hz. At the moment due to my computer situation and cable availability, the Mac mini is still plugged into the monitor as it always was with a USB-C→DisplayPort and the MacBook Pro, via the OWC dock, with Mini DisplayPort→HDMI. At some point I will banish the Mac mini from the 4K monitor (it gets little direct use and can survive with just a 1080p one) and switch the MBP to pure DisplayPort, which of course means I need a new cable. However, it is interesting to note that the Mac mini rarely managed to cope if it started with the monitor off and while that does happen occasionally with the MBP, most of the time it wakes the monitor up just fine. So I’m not sure moving it to DisplayPort will be all wine and roses.
Oh I have other reasons to boot it out. Major backlight leakage in the corners and now I note along the edges.
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My reading is that the limit depends on the HDMI cable and the specs of the output/input systems.
I am going to swap to a display port cable at some point.
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JJW
My bad. I think I was reading dock specs. I just checked and my OWC USB-C dock’s Mini DisplayPort only supports 30Hz. I was concerned about refresh rate but honestly I don’t notice any problems. Probably my fears hark back to CRT days when a slightly-too-low refresh rate meant headaches.