Macintosh HD and Macintosh HD Data?

That's normal. The Mac HD - Data volume is where your files and apps are kept and you have access to them just like the older system volumes.

The Macintosh HD volume is where the system and system support files are kept and the user has no access to them. It's part of the new security that Catalina brings to the table.

What version of Catalina are you running? I have Version 10.15 (19A602) and only the -Data volume is shown in the Finder or in the Storage section of About this Mac but both are shown in Disk Utility.

My inquiry is different. I upgraded from Majove to Catalina , but then I determined that Catalina was not working as satisfactorily for my needs as Mojoave. I then reinstalled Mojave. However, I still have both a HD and HD-Data folder characteristic of Catalina, but not Mojave. The computer works fine so far, but the HD-Data did not exist on my Mojove system (according to earlier versions of Mojave backed up on my external hard drive) before I upgraded to Catalina and then reverted to Mojave.

My questions are:

1. Are there risks to my computer in keeping this current configuration, which was designed for Catalina?
2. If there are, how do I remove the HD-Data folder?

Thanks for any guidance that you can offer.

I'm having the same issue with my MacBook Pro 2017...I have no memory and this computer has virtually nothing on it. Just started using a Seagate Backup that tells me it can't catch screen shot and it hasn't resolved my issue, not even sure it is working. Still getting message about my disc is full. Can anyone assist as to how a computer that has hardly any files on it, transferred photos to external back, zipped files, no music, no movies, no games still has no memory?? I have Mohave 10.14.6 with 8 gb memory, should be just perfect for my business needs. Super frustrated with this computer it not living up to apple standards by any means. Any help would be really appreciated thanks!

Boot into Safe Mode (Use Safe Mode to isoloate issues with your Mac) with both drives connected and start a backup to see if both get backed up. Then reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing. 

Well, I hope no one takes your advice. When you install Catalina all of your data is put into the Data partition, and only Catalina itself is in Macintosh HD (where it is write protected). So if you delete the data partition (Macintosh Data) you will delete all of your data.

And if you just delete the data partition the remaining space on the physical drive does not automatically get reassigned to the Macintosh HD partition; it becomes unusable space. To recover that space you need to undo the partitioning: https://support.apple.com/en-us/HT208496, then restore Time Machine.

Could you please tell me what you mean by 'reinstall correctly"

Here are the instructions on how to erase a disk which has Catalina installed.

https://support.apple.com/en-us/HT208496

And do look at lkrupp's explanation of the new filing system (eloquently explained).

FWIW, I have not ever seen a warning like that (your screenshot), so I do not know what that is except to guess that it may also have to do with something the new APFS did not allow.

I recently upgraded my parents' 2017 iMac and encountered a similar yet different issue. I understand the need for a Mac HD and Mac HD - Data as part of the security of Catalina, but the machine ended up with 2 drives called "Mac HD - Data" after the upgrade. (To be fair I'm not certain it wasn't this way prior, but Time Machine is giving an error on backup related to the "duplicate" drives so I believe it's new.) Has any once else encountered this? Any ideas to solve? The top two volumes in the screen shot below clearly indicated Mac OS 10.15; the last one (selected) doesn't have any OS designation.

I updated to Catalina and decided I didn't like it, so I restored from the last Mohave backup. It seems that both the Macintosh HD and the Macintosh HD - Data have the same amount of storage used, almost as if data files got stored into both internal storage hard drives. Like the information was doubled.

I updated to Catalina and decided I didn't like it, so I restored from the last Mohave backup. It seems that both the Macintosh HD and the Macintosh HD - Data have the same amount of storage used, almost as if data files got stored into both internal storage hard drives. Like the information was doubled.

Could you please tell me what you mean by 'reinstall correctly"? Please understand that I mean absolutely no sarcasm here. There seems to be a good chance that I will receive the same error that I am getting now, shown in the graphic below, if I were to reinstall incorrectly. I fear the issue that I presented in my first posting, and this issue are related

If I search concerning this issue on the internet, the answers state that if all other solutions fail, I should reinstall the OS as a last resort to make this error go away. I have tried every solution I a can find, and fear that reinstallation could be repetitious if I don't understand the issues presented here and in the previous email

Thank you for your time.

There is something wrong - there is no way Apple takes half of a 2 TB drive for the OS - that Mac HD portion is normally quite small - mine is less than 12 GB:

So, can you post more details and provide screenshots please.

Hi,

I made two separate volume so that I can easily update my OS if in case a problem occur. Here's how it looked like if I view it from the 'Storage'.

However, after updating to macOS Catalina, 10.15.4, The HD Volume created additional Volume which is 'HD - Data'. What should I do with this? Should I delete 'HD - Data'? How do I clean install the new OS in my laptop?

Additional question, how do I transfer my backup file in a hard drive ntfs format?

Thank you.

Yes, I erased the disk before reinstalling.

FINDER:

Note that the HD-Data disk is empty. All my data is on the MAcintosh HD. This is not what apple says - "macOS Catalina runs on a dedicated, read-only system volume called Macintosh HD. This volume is completely separate from all other data to help prevent the accidental overwriting of critical operating system files. Your files and data are stored in another volume named Macintosh HD - Data. In the Finder, both volumes appear as Macintosh HD. "

Also note that the finder says that the Macintosh HD-Data has a size of 864 KB while Disk Utility says it has 499.96 GB. Disk utility also says that the HD-Data disk is using 119.34 GB while the Finder shows it to be completely empty, and shows all my data on the Macintosh HD. disk.

But now as I look at the Disk Utility I see that it claims I have 2 Macintosh HD-Data disks. The 2nd one has 499.96 GB but only 885 KB are used and there is 132.18 GB on "Other volumes"

All very strange. But clearly the Finder thinks that all my data is on the Macintosh HD and not on the Macintosh HD-Data.

I would love to hear a clear explaination of all this.