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User profile for user: Airsculpture
Airsculpture Author
User level: Level 4
1,642 points

Currently running Big Sur on External but Internal Drive will be Mojave

As the title suggests I am currently running Big Sur on External SSD but reformatted my Internal drive doing an internet recovery to it's original Mojave version.


The internal drive is a standard HDD so I formatted it as Mac OS Extended with GUID Map. I noticed once the installation was complete that the drive is Mac OS Extended with GUID Map but when I click on the Macintosh HD inside the Container in Disk Utility this states it is a APFS Volume.


Is this correct or normal ?

Should I have formatted the whole internal drive as APFS instead of Mac OS Extended with GUID Map ?


At the end of the day it makes no difference to me as I'm using the external SSD with Big Sur on it but I would like the answer so that I can have it set up correctly.


Attached screenshots.

iMac 21.5″, OS X 10.11

Posted on Jan 27, 2021 9:41 AM

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6 replies
User profile for user: Sharhari
Sharhari
User level: Level 5
6,293 points

Jan 28, 2021 4:42 AM in response to Airsculpture

Please see "Start up your Intel-based Mac in macOS Recovery" in below link.

Use macOS Recovery on an Intel-based Mac - Apple Support


  • Option-Command-R: Start up from macOS Recovery over the internet. Use this key combination to reinstall macOS and upgrade to the latest version of macOS that’s compatible with your Mac.
  • Option-Shift-Command-R: Start up from macOS Recovery over the internet. Use this key combination to reinstall the version of macOS that came with your Mac or the closest version that’s still available.


I'm not sure what is your mac model and macOS it came with, hope above info helps.

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User profile for user: Matti Haveri
Matti Haveri
User level: Level 6
16,643 points

Jan 28, 2021 4:33 AM in response to Airsculpture

Mojave install and updates insist on APFS.


On the other hand, Mojave can be cloned (with Carbon Copy Cloner etc) and it runs OK on a Mac OS Extended. The only drawback is that the updates don't work so you'd have to update running an external APFS volume and then re-clone that. There should be not many Mojave updates, though.


Spinning HDDs tend to be quite slow with APFS. They are OK as Mac OS Extended archive disks or High Sierra and earlier.

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User profile for user: Airsculpture
Airsculpture Author
User level: Level 4
1,642 points

Jan 28, 2021 4:38 AM in response to Matti Haveri

OK. Thanks.


As I said, I'm not actively using the internal drive with the iMac. I boot off one of two external SSD drives, one Big Sur the other Catalina, so really I'm only putting a fresh install on there so that the internal has an OS. Possibly use the remainder as storage but don't really need it. Both SSDs are 500GB and my iTunes is on a 5TB external drive.


Just wanted to know the formatting for the fresh install.

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Currently running Big Sur on External but Internal Drive will be Mojave

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