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Question: Can't format an ext. drive? High Sierra/AFPS issue?

For some reason, I'm unable to format an external HD.

Is this because I've upgraded to "High Sierra?" The new "AFPS" file system?


  • I've tried TWO DIFFERENT, brand new external HD's (a trusted brand of bare drives that I use for archiving)
  • Neither would format on my iMac nor my MBP!
  • Tried "Disk Utility>repair and/or format, etc. (MacJournal, ExFat...)
  • Quite simply the disks are not recognized by my both of my Macs.
  • Older HD's that have already been formatted (same brand) are still recognized
  • Reiterating, I sent back the first drive thinking it was defective. I was sent a NEW one. Same issue.

The ONLY variable I can think of is, I have updated to High Sierra since I last formatted this brand of HD's.

iMac (27-inch Mid 2011), macOS Sierra (10.12.3), 3.4Ghz Intel i7 32GB FCPX 10.3.2

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Sure he means Disk Utilities and from the menubar select View> Show All Devices.

you should now see the Disks and not just the Volumes. Format the Disk as you have done in the past.

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Nov 14, 2017 4:11 AM in response to dastoelk In response to dastoelk

Restart using command-r. Go to utilities to see all connected drives. If they do not show click on the menu item "show all". This is new in High Sierra. Once they appear you can format them and then they should work. I had a the same issue.

Nov 14, 2017 4:11 AM

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Nov 14, 2017 11:01 PM in response to Eau Rouge In response to Eau Rouge

I'm sorry. I appreciate your response, but... I don't think you read my post closely. I tried all of that. (With "Disk Utility. I am quite familiar with formatting HD's.) However, since upgrading to High Sierra, an external HD (no matter if "new" / "old") is not recognized by my mac. "tbirdvet" wants me to do a "restore" and, then, go to "Utilities." But, I am unsure if he means going "back" to "disk utility." (As you show in your screen shot.)

Nov 14, 2017 11:01 PM

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Nov 17, 2017 8:10 PM in response to James CH Henderson In response to James CH Henderson

James CH Henderson: I was just able to format a HD using the above methods successfully. (Booting up in recovery mode, then going into Disk Utility > show all drives.)

One more thing: I found that I had to physically remount the hard drive, after booting up in recovery mode, for it to reveal itself. This is to say, I inadvertently left the drive connected to my Mac when I went into recovery mode. But, once in recovery, I ejected/re-inserted the drive and it showed up if Disk Utility.

I will have to agree with you that "something is wrong here." This may very well have to do with High Sierra.

Good luck.

Nov 17, 2017 8:10 PM

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User profile for user: dastoelk

Question: Can't format an ext. drive? High Sierra/AFPS issue?