Macintosh HD and Macintosh HD Data?

People need to get educated about both Catalina and APFS, especially APFS. With APFS the term ‘partitioning’ no longer applies. APFS (Apple File System) has replaced HFS as the default. APFS creates what is called a ‘container’ which ‘contains’ the entire hard drive it is installed on. The user then creates ‘volumes’ within the ‘container’. The volumes appear to have the same storage space when, in fact, they are actually sharing the same space on drive. That’s how APFS works and it’s totally different than the previous file system HFS/HFS+. Apple now recommends creating an APFS volume instead of partitioning (although you still can if you want to). Creating and removing volumes on an APFS formatted drive is much easier and faster than adjusting partitions. When you remove an APFS volume its contents are erased and that space is immediately available to any volumes remaining in the APFS container.

So no, Apple did not totally ‘screw up’. People need to educate themselves how both Catalina and APFS work. Thinking as if everything is the same is the best way to get into real trouble.

So does that mean I have to delete the current container In the recovery mode, or some other way, before I do an installation again as recommended here, or does the new installation do that for me?

If the new installation does not delete the current container setup before installation and provide a new container setup, then I will in fact get the same errors I am getting now right ?

so I may end up installing the os a few times and not have access to my computer until I get to go to the apple store?

i don’t think reading the documentation will help me put this problem in context. Again I could really use some help here. I don’t think that RTFM will do.

thanks again,

bob

Will a new installation do that for me?

Will a new installation do that for me?

Will it do what for you?

Reading up and educating yourself makes us who and what we are.

Installing OS X over a current OS install will simply install an OS over what you currently have. It does not automatically erase anything.

Unless you erase the drive, you will most likely have the same problem.

You do not need the app store for this because you are going to use recovery which means you will download whatever from Apple's servers directly.

You never really had a problem in the first place. Disk Utility should show Both an HD and a Hd Data. That is normal and required for Catalina. When you tried to change back to Mojave, you had already changed the file structure on your drive which is probably why you couldn't easily get back to not having the 2nd partition. This is why you probably had to re-format the disk. Tell me, did you reformat in Mac OS Extended or APFS.

What I would like to understand, is why I bought a 2TB Macbook Pro, yet Apple decides to take HALF the drive just for the operating system? So I get 1/2 the advertised drive space??? Do we really need 1TB for Catalina? Is there a way to extend the partitions so i can make the Data partition smaller?

Do we really need 1TB for Catalina? Is there a way to extend the partitions so i can make the Data partition smaller?

My system is about 11 GB, much like babowa's.

I think you don't understand the display your are reading, or it is just the standard misinformation in the Storage displays in macOS.

Why would you want the Data Volume smaller? It doesn't matter, anyway--the same storage space is shared amongst all volumes in the container.

What do you want to do with your data in order to make the Data volume smaller? Do you not want your data stored on the startup drive?

If you delete HD - Data all of your non-system content will be deleted. As explained earlier in this thread Catalina splits the system disk into a write-protected region that contains system data and a “normal” region for everything else. If you change the view to see containers this will become more apparent. Your HD 2 was not affected by the update to Catalina.

Even if you do a fresh install with Catalina, you will get two volumes and one will be the Data volume. It contains everything except your OS/system files. So, YES, you need that - do not delete. Those two volumes are a new Catalina feature for security reasons and they are part of your Mad HD, only visible in Disk Utility.

Additionally, it is an inherently bad idea to partition your hard drive to have a backup partition on the same disk. If and when your drive fails, it will also wipe out your backup. You should always have your backup on a separate drive.

Same scenario here, did a time machine backup, disconnected TM drive, then upgraded from Mojave to Catalina. Tried it, didn't like it, so reconnected TM drive and used normal Recovery process to go back to Mojave. The machine worked ok but I had the extra Data drive apparently with 230Gb of info on it. Apple support recommended completely erase drive then restore from TM backup. I could have chosen this path and wasted another 4 hours, and it was an option as a last resort... HOWEVER, using info from this thread I was able to fix the problem in about 5 minutes, without even using Safe Boot.

First, I typed "Startup" into the finder search field.This opened System preferences and confirmed my actual startup disk was the SSD drive, and not SSD-Data. So, open Disk Utility, select the SSD-Data drive and Unmount it, then Erase it. The system will automatically remount it after the delete, so Unmount it again, then select "Delete APFS Volume" from the menu options.

In an instant the SSD-Data drive had gone and the Gigabytes of assigned storage were re-assigned to the one and only Mojave startup drive. Job done.

Catalina is just too big a jump for me, too many apps wouldn't work and the cost of upgrading from Adobe CS6, Office 2011is not viable for me. Worst of all "Freecell" doesn't work! Sorry, Apple, Mojave will be my last OS.

Hope this info helps others stuck with 2 drives after reverting to Mojave from Catalina.

Old Toads answer is what Apple Support says in the document "About the read-only system volume in macOS Catalina". But that does not seem to be the case for my computer, a new macBook Air. Because of problems with Accessebility-Dictation, I had to reinstall the OS. It created the 2 disks you mentioned, but all my Data, Users, and all my files, as well as the system, is on the "Macintosh HD". The Disk " Macintosh HD - Data" is blank, completely empty, "0 Items, 377.72 GB".

So, what is going on here?

If you are saying you want to go back to Mojave and restore your drives to their previous state, then here are the steps I took to fix the issue, copied from elsewhere in this thread, hope it helps.

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NOTE WELL, THIS IS EXTREMELY IMPORTANT.

I TOOK THESE STEPS AFTER RESTORING MOJAVE FROM MY TIME MACHINE BACKUP.

DO NOT DELETE THE DATA DRIVE IF YOU STILL HAVE CATALINA INSTALLED. YOU HAVE BEEN WARNED!

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"Apple support recommended I completely erase the drive and then restore from TM backup. I could have chosen this path and wasted another 4 hours, and it was an option as a last resort... HOWEVER, using info from this thread I was able to fix the problem in about 5 minutes, without even using Safe Boot.

First, I typed "Startup" into the finder search field.This opened System preferences and confirmed my actual startup disk was the SSD drive, and not SSD-Data. So, open Disk Utility, select the SSD-Data drive and Unmount it, then Erase it. The system will automatically remount it after the delete, so Unmount it again, then select "Delete APFS Volume" from the menu options.

In an instant the SSD-Data drive had gone and the Gigabytes of assigned storage were re-assigned to the one and only Mojave startup drive. Job done. "

I keep getting Macintosh HD - Data AND Macintosh HD - Data - Data showing up on my desktop - both empty. Time machine will not backup unless I delete both of them which I do but they both show up again in a few days.

Maybe it's an "is what it is" issue.

alwyzgr8tful wrote:

I'm having the same issue with my MacBook Pro 2017...

I'm not sure what issue you think you are having, but you Data drive is not mounted. Since it isn't mounted, you would not be able to see your data.

The storage display for Macintosh HD (the OS) indicates that your drive is completely full. With an SSD, that is extremely bad. It will take forever for it to reclaim any free space made by deleting files.

Why the data drive is not mounting is concerning. There may be something wrong with the drive (besides it being full).

If you select it and click the Mount button, does it mount or produce an error.

You should probably create an entirely new post for this issue as it will likely take away from this thread trying to resolve your issue.

I’m not having any issues except to confirm what others are reporting. empty phantom hard disk or disks randomly appear on my desk top preventing my time machine backup from working. These hard drive images are empty so I simply “unmount” them when the appear. Happens every few weeks but since unmounting then fixes time machine back ups - I just keep doing this work around.