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OS Catalina. 2 MAC HD data drives

After installing Catalina a second time, it put a second Mac HD data partition. Then when trying to use Time Machine, it failed. Because there are two drives with the same name HD data. How do I rename the drive or delete the Drive. How do I know which one Catalina is using?

iMac Line (2012 and Later)

Posted on Oct 11, 2019 4:26 PM

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Posted on Oct 31, 2019 8:30 AM

Finally an answer ;

  1. back up your computer
  2. power off then; enter recovery mode with the world spinning
  3. select disk utility
  4. show all devices; erase both hd data drives one at a time
  5. select the Hard drive top layer; erase the drive
  6. power off and open again in recovery mode and download Catalina
  7. then restore your data from time capsule


everything is back to normal

after talking to a senior analyst ; the drives must be erased before installing catalina; otherwise it will just keep install new ones with the old data drives.

47 replies

Dec 2, 2019 7:51 AM in response to vincentfromprt

I would only use the last back up; the back up that only contains one drive. However, you can use the finder to change the name of one of the HD data drives. Allowing time machine to back up. This only changes the name that YOU see. Not the name that Catalina is actually using for its HD data.


of course, the risk is: you are copying the same problem and inserting it after you have cleaned everything up. Especially, if you look at the HD data drive and it has already created a new container and or volume.


do you not have a good back up before the problem started?

copying the problem, will most likely create another problem.

Dec 2, 2019 8:03 AM in response to gchdrake

Apple has confirmed, that renaming the drive just exacerbates problems.

basically, starting fresh, with an old back up, which was known to be good is useful.


to answer one of your questions: you can look up the time and date in finder through GET info, about when the drive was created.


The main reason, I had to start over was: each data drive had created another volume and container, which doubled the memory usage. The easiest way is to remove everything off the computer, via the steps, and then repair with the backup before the problems. My iMac is working great and fast as advertised in Catalina.






Dec 7, 2019 9:07 AM in response to craig150

I have the same issue. I named the second data partition ghost. And that's that. Look at the size. Mine is 1mb (go to time machine exclude the duplicate partition and it says how big it is). It's not a real partition.


My advice. Hide it and forget about it - unless you need that get that 1mb back. Probably it will get fixed in an update later on. Why risk your system or spend hours on a fresh install.


It's a ghost :-)

Jan 12, 2020 3:38 AM in response to Harry Cover

Answering to myself (hope it helps):

Catalina is installed on a dedicated read-only system volume, while your files and data are stored separately in another volume labelled with the suffix "- Data."


The idea behind this setup is that it helps prevent the accidental overwriting of critical operating system files, since the user can no longer alter data or store files on the read-only system volume.


In practice, the average user shouldn't notice any difference after the split, since both volumes appear in Finder as a single unified volume

OS Catalina. 2 MAC HD data drives

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