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User profile for user: frustratedW1H
frustratedW1H Author
User level: Level 1
4 points

Formatting a Toshiba external drive for macOS Big Sur

I want to use this drive on my new MacBook Pro. It has always worked on my old MacBook Air on which I used the Toshiba encryption on it. I followed the instructions for initialising it on the Pro and it failed with these messages:


Erasing "TOSHIBA External USB 3.0 Media" (disk4) and creating "Toshiba 2T"


Unmounting disk

Creating the partition map

Unable to write to the last block of the device. : (-69760)


Operation failed...


After several attempts I put the drive back onto the Air and erased it there. I then tried again on the Pro and got the same message. Would really appreciate any suggestions.

MacBook Pro 13″, macOS 11.6

Posted on Oct 3, 2021 5:11 AM

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User profile for user: frustratedW1H
frustratedW1H Author
User level: Level 1
4 points

Posted on Oct 3, 2021 7:47 AM

The disk was encrypted using the Toshiba encryption software provided with the device but when I tried to remove the encryption the software didn't provide the function to do it though it showed it in the documentation. I then completed an erase action on the original MacBook Air.

In answering all your questions I reconnected to the Air and went back into the Toshiba encryption app to be sure of my facts. It seems that given the drive has no data, it was able to provide the means to remove the password protection. Tthe drive is now recognised by my Pro without the need to reformat.

Thank you for stimulating me to keep trying.

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User profile for user: frustratedW1H
frustratedW1H Author
User level: Level 1
4 points

Oct 3, 2021 7:47 AM in response to Matti Haveri

The disk was encrypted using the Toshiba encryption software provided with the device but when I tried to remove the encryption the software didn't provide the function to do it though it showed it in the documentation. I then completed an erase action on the original MacBook Air.

In answering all your questions I reconnected to the Air and went back into the Toshiba encryption app to be sure of my facts. It seems that given the drive has no data, it was able to provide the means to remove the password protection. Tthe drive is now recognised by my Pro without the need to reformat.

Thank you for stimulating me to keep trying.

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User profile for user: Matti Haveri
Matti Haveri
User level: Level 6
16,673 points

Oct 3, 2021 5:52 AM in response to frustratedW1H

> any suggestions


Select the whole device (not just the volumes under it) via Disk Utility > View > Show All Devices and erase it as MSDOS-FAT (Master Boot Record partition scheme). Might not be necessary but that might clear some junk.


Then erase it in a similar way to the desired format, usually MacOS Extended-Journaled (GUID partition scheme) for HDD or APFS (GUID) for SSD.

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User profile for user: frustratedW1H
frustratedW1H Author
User level: Level 1
4 points

Oct 3, 2021 9:46 AM in response to PRP_53

Yes, I'm sure that it will be fully functional. It is presently running a Time Machine backup on the new Pro. I previously copied a directory from my hard drive to check its functionality. All seems to be well, thank you.


The problem seems to have been that the Toshiba encryption software would only allow me to remove encryption when I had erased all the data, unlikely as that may sound.


My thanks to all who offered their help.

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Formatting a Toshiba external drive for macOS Big Sur

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