![]() ![]() After trying a few things – finding and killing a fsck process which had a handle on it worked for me: $ ps -ax | grep fsck $ sudo kill Īfter that – the disk became available again and I could Erase it in Disk Utility. A bit of googling revealed this was because some process had a hold of it possibly Spotlight, possibly something else. Then to unmount it: $ sudo diskutil unmountDisk /dev/disk1įorced unmount of disk failed at least one volume could not be unmounted The Fix On my machine the 4TB WD Elements was /dev/disk1. Next step then was to force it to unmount from the command line. Unfortunately – Erase complained as it couldn’t unmount the disk in the first instance – just giving a ‘Couldn’t unmount disk’ message. I don’t mind losing the data – I just want a working drive back… Couldn’t Unmount Disk I tried a Verify, and then a Repair – which initially looked promising as it found a problem… but then it said it couldn’t repair and I should consider reformatting. Success! I could at least see the drive in Disk Utility now. The next thing I tried was plugging the drive into an older Mac Book Air I have (which was running an older version of macOS). A bit more digging revealed the drive could be seen in System Report (via Apple logo on menu. The drive was still invisible to Finder and Disk Utilities. So the first thing I did was update the OS (to High Sierra – as it turns out – a pretty substantial upgrade). A quick google revealed this wasn’t uncommon, and a couple of posts mentioned issues with Sierra. Whatever I did – I couldn’t get the new 4TB drive to show. Lights were on and flashing, but now they were not visible in Finder.Ĭue several attempts and unplugging, replugging, restarting the computer. The connection was flimsy – so I figured they both just lost power and reset. I then plugged another WD Elements (an older 500GB one) into one of the other USB hub ports – and both drives disappeared from Finder. I could see the files on the drive – I even moved a couple of folders successfully on the new drive. When I got back from work it looked like it had finished ok. The 2TB transfer was left overnight and during the day. The MyBook Duo used the official Apple Thunderbolt adapter – which is pretty solid, and the WD Elements was plugged into a 3 port USB hub – which is a bit flimsy. Its a 2017 model so has no native USB or Thunderbolt 2 ports – just USB-C, so I had to use adapters to plug in my drives. I formatted it and started with a 2TB backup of my 4TB (2x2TB RAID1 WD MyBook Duo). I recently bought a 4TB Western Digital Elements external drive in the Black Friday sales to add to add to my backup family. Whatever you do, don’t unplug the USB cable willy-nilly.A tale of a brand new disk drive, a 2TB backup, a disk failure and finally a recovery… While this won’t help you in your current predicament, there is a simple bit of advice you can follow to help avoid data corruption: always disconnect your drive safely. There are too many to cover here, but our sister site Macworld UK outlines theīest data recovery apps for those interested. ![]() These are generally paid apps, but they could restore your external drive depending on the issue. If all else fails, you’ve always got the option of using a third-party data recovery app. Reformatting an external drive for Mac in more detail separately. Click Erase to confirm and start the reformatting process.Only fast external SSDs can utilise APFS formatting. If you want to use the drive across PC and Mac, we’d recommend ExFAT, but if you’re on macOS exclusively, we recommend Mac OS Extended (Journaled). Enter a new drive name and select the new format.Select the external drive from the list on the left.Plug your external drive into your Mac.When you’re ready to reformat the drive, follow these steps: We’d recommend using a PC to transfer files prior to reformatting the drive for use with Mac where possible. The good news is that it’s easy to change the format – the bad news is that doing so will completely wipe the drive, deleting any previously-stored data. ExFAT: Upgraded version of FAT32 without file limits, compatible with PC, Mac and Linux.Ĭhances are that if your drive is recognised on PC but not Mac, it uses the NTFS file format.FAT/FAT32: Older file format limited to a maximum 4GB file size, but compatible with PC, Mac and Linux.APFS: File format introduced in macOS Sierra, not compatible with PC. ![]()
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