Disk utility will not fully erase all memory on external drive

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Level 1

8 points

Disk utility will not fully erase all memory on external drive

I used Disk Utility to erase external drive and I'm puzzled why it shows 60% of the space free and 40% of memory "used." Notice the 144 MB mystery memory that will not erase in the screenshot.

Running Big Sur 11.1. I suspect that this has something to do with using the same external drive as Time Machine back up on two different Macs in my house. I've tried turning off automatic back up of Time Machine, and I've already tried running Disk Utility to erase this external drive on both computers already.

One machine is Mac Mini M1 and the other is Macbook Air, both are brand new. Guidance appreciated

Posted on Jan 24, 2021 12:24 PM

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Answer 1

Top-ranking reply

den.thed

Level 10

91,834 points

Jan 24, 2021 4:20 PM in response to CCSprings

Jack-19 is spot on. The small 144MB partition is normal.

Plus there is no reason to format the External HD APFS, unless you are going to install macOS.

If you want it to only show one partition, then you need to format it Mac OS Extended (Journaled) instead of APFS.

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Answer 2

Jan 29, 2021 12:50 PM in response to CCSprings

Instead of "Erase", select Partition instead and see what it shows.

It is possible that somehow the "missing" GBs got released as

"free space" and I don't believe that the "Erase" function will

coalesce that into currently partitioned space.

Another thing to try, select the top level drive, WD Elements....,

and do a repair disk. One possibility is that the partition table

is messed up and the repair disk may fix it.

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Answer 3

Jack-19

Level 8

46,254 points

Jan 28, 2021 4:25 PM in response to CCSprings

First, when you erase, did you erase the top WD Elements 1042 Media as APFS and GUID Partition Map? Try that again.

If it persists, I would call Western Digital and see what is going on.

Cheers,

Jack

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Answer 4

Jack-19

Level 8

46,254 points

Jan 24, 2021 4:09 PM in response to CCSprings

Hello CCSprings,

Based on your screenshots, it appears that your drive is fully erased. All erased drives may have a small used portion on them, always under a GB. However, I am not seeing these 60% and 40% values you are talking about. This drive appears to be erased and ready for use.

If you have questions, please post back.

Cheers,

Jack

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Answer 5

CCSprings Author

Level 1

8 points

Jan 28, 2021 4:22 PM in response to Jack-19

Great question - no it does not show as 1TB on other Macs. I tried to fully erase the external drive on both of my Macs. I even went back to my original purchase receipt from years ago to make sure it was 1TB. Here is another clue, this is happening on both of my 1 TB external hard drives which I use for Time Machine. In frustration I finally took one of the external drives and performed "disk clean up" using my work laptop which is a Windows 10 machine. Bam - - - clean to 1 TB! Why can't Apple do that? I'm an Apple fan!

I still have one external hard drive for experimentation and to advance our science here. What next?

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Answer 6

CCSprings Author

Level 1

8 points

Jan 28, 2021 4:08 PM in response to den.thed

I see what you are saying here. What I neglected to mention is that this is a 1TB external hard drive. Why is only 320 GB free?

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Answer 7

Jack-19

Level 8

46,254 points

Jan 28, 2021 4:10 PM in response to CCSprings

Well, it is certainly not showing as 1TB. Does it show as 1TB on your other Macs?

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Answer 8

CCSprings Author

Level 1

8 points

Jan 29, 2021 12:22 PM in response to Jack-19

Hi Jack! Yes, I did do that. Just to be 2x sure per your suggestion I tried it again. You can see it is showing 320 GB free (blue) no 1 TB. No improvement. I'll try Western Digital next.

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Disk utility will not fully erase all memory on external drive

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