External SSD screwed up

[isza41]

Hello, I got an external 4TB SSD for backing up photos from my mobile phone. Unfortunately, I did something stupid with it, and now Disk Utility can not repair it: it says, it is uninitialized, but when I want to initialize it, it marks an error. I would like to format it for my Mac. What can I do?

 

[Lufbrarunner]

Hello, I got an external 4TB SSD for backing up photos from my mobile phone. Unfortunately, I did something stupid with it, and now Disk Utility can not repair it: it says, it is uninitialized, but when I want to initialize it, it marks an error. I would like to format it for my Mac. What can I do?

My friend Claude says:
This is a common situation, and there are a few things to try in order. The “uninitialized” message usually means the partition table or header is damaged or missing, and the error on initialising is often down to how Disk Utility is looking at the drive, not the drive itself.

1. Rule out the boring causes first

• Try a different USB cable and a different port (ideally directly on the Mac, not through a hub). Flaky connections cause exactly this kind of error on initialise.
• If the SSD has its own USB-C and USB-A cable options, try the other one.

2. Show the whole device in Disk Utility

• Open Disk Utility, go to View > Show All Devices.
• Select the top-level physical drive (the manufacturer’s name, not the volume underneath) and choose Erase.
• Pick APFS (or Mac OS Extended if you need compatibility with older Macs) and, importantly, GUID Partition Map as the scheme.
• Erasing the top-level device rewrites the partition table, which is usually what an uninitialised drive needs. Initialising only a volume often fails.

3. If that still errors, use Terminal
Find the drive:


diskutil list
Look for the external 4TB disk (e.g. /dev/disk4). Double-check the size and that it’s the right one, because the next command wipes it:


diskutil eraseDisk APFS BackupSSD GPT /dev/disk4
Replace disk4 with your actual identifier. If it says the disk is busy, run diskutil unmountDisk force /dev/disk4 first and retry.

If it’s still stubborn, you can zero the start of the drive to clear whatever is confusing it, then repeat the erase:


sudo dd if=/dev/zero of=/dev/rdisk4 bs=1m count=100
Again, be certain of the disk number. A mistake here wipes the wrong drive.

4. If nothing works

• Try the drive on another computer (even a Windows PC) and see if it appears in Disk Management. If it does, you can often clear and repartition it there, then reformat on the Mac.
• If it isn’t detected at all, or errors out everywhere, it may be a hardware fault, and the warranty is the next step.

Important caveat about the photos: every step above erases the drive. If there’s anything on there that isn’t backed up elsewhere, stop before erasing and try recovery software first (Disk Drill, TestDisk, or PhotoRec, the last two being free). Recovery chances are best if nothing has been written to the drive since the problem started.

It would also help to know what the “something stupid” was (for example, pulling the drive mid-write, or a failed partitioning attempt), since that points to whether the damage is just the partition table or something deeper.