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2 Macintosh HD partitions after clean install

I have tried repeatedly to merge my partitions into one HD but for reason it continues to return. Even after wiping and doing a clean install of macOS. How is this possible? Also, this problem seems to be associated to all my Mac computers. It is very annoying. I do not like it and want to get rid of the 2 partitions and merge them into one. I searched the Internet for some advice and have come up empty. I've tried deleting one of the partitions and I always end having to reinstall macOS and the 2 partitions return. This almost seems like an infection of some sort. Has anyone experienced this? I have 2 macs running Monterey and one with Big Sur. The issue affects them all.

MacBook Air (2020 or later)

Posted on Apr 3, 2022 11:18 AM

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Question marked as Top-ranking reply

Posted on Apr 3, 2022 11:43 AM

HI there FBNMRNO I understand that you have a question about the partition map of your hard drive and Id like to see if I could help with that. There could be a few different things occurring so I'd like to clarify a few things if i could. Since you mentioned that all your macs have this occurring its likely the case that you are viewing volumes within the container disk rather than partitions of the hard drive. More on that below. The next possibility, but i highly doubt it, could be that you are running a fusion drive that has split. If this is the case when you go into About this Mac > storage, you would see 2 hard drives, a large HDD and a smaller SSD. If this is the case then you can repair that by following these steps here, don't forget to back up your hard drive first tho.


If youre seeing Macintosh HD and Macintosh HD - Data then from within the disk utility app, then nothing is wrong with any of your macs, thats how its supposed to be formatted. If that is in fact the case, then your mac is using APFS which is significantly different than the previous files system. In APFS there are volumes inside container disks that are all free to share the space that the container disk is allotted. Partitions would have a set amount of space they could consume, moreover, data cannot flow across partitions like it can within the volumes in APFS. You'll see in disk utility on your mac running macOS Monterey after you click on view > show all devices, that the operating system has its own volume, and your data has another. Theres a lot more on this here, here and here.


I would suggest to stop erasing or deleting the volume because you will continue to relive the same ground hog day reinstall over and over. I hope this helps, feel free to ask any questions you have and ill check back later today to see if I can help!

3 replies
Question marked as Top-ranking reply

Apr 3, 2022 11:43 AM in response to FBNMRNO

HI there FBNMRNO I understand that you have a question about the partition map of your hard drive and Id like to see if I could help with that. There could be a few different things occurring so I'd like to clarify a few things if i could. Since you mentioned that all your macs have this occurring its likely the case that you are viewing volumes within the container disk rather than partitions of the hard drive. More on that below. The next possibility, but i highly doubt it, could be that you are running a fusion drive that has split. If this is the case when you go into About this Mac > storage, you would see 2 hard drives, a large HDD and a smaller SSD. If this is the case then you can repair that by following these steps here, don't forget to back up your hard drive first tho.


If youre seeing Macintosh HD and Macintosh HD - Data then from within the disk utility app, then nothing is wrong with any of your macs, thats how its supposed to be formatted. If that is in fact the case, then your mac is using APFS which is significantly different than the previous files system. In APFS there are volumes inside container disks that are all free to share the space that the container disk is allotted. Partitions would have a set amount of space they could consume, moreover, data cannot flow across partitions like it can within the volumes in APFS. You'll see in disk utility on your mac running macOS Monterey after you click on view > show all devices, that the operating system has its own volume, and your data has another. Theres a lot more on this here, here and here.


I would suggest to stop erasing or deleting the volume because you will continue to relive the same ground hog day reinstall over and over. I hope this helps, feel free to ask any questions you have and ill check back later today to see if I can help!

Apr 4, 2022 2:18 PM in response to FBNMRNO

FBNMRNO wrote:

I have tried repeatedly to merge my partitions into one HD but for reason it continues to return.


If you are running Catalina or any later version of macOS (Big Sur, Monterey ...), your system drive is formatted as APFS. The default configuration of the APFS system drive contains one Container (aka partition): that contains two Volumes called Macintosh HD and Macintosh HD - Data. This is normal and you cannot merge them. Macintosh HD is the sealed system volume and you cannot change it; Macintosh HD - Data is where user-modifiable files reside including user-installed applications and user home folders.


On the other hand, if your drive is physically partitioned with 2 or more hard partitions and you reinstall macOS, the reinstallation will only affect the 1 partition you are installing to. The 2nd (physical) partition would remain untouched. If you want to remove a 2nd physical partition you will have to use Disk Utility while booted into Recovery Mode.

2 Macintosh HD partitions after clean install

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