Is possibile to move /Syetem/Volumes/Data parition to other disk in Catalina or newer?

I would not advise doing it that way even if possible. It's clear you want to use your Disk 2 for data. Just format it as APFS (if it's an SSD) or Mac OS Extended Journaled (if it's an HDD) and use it for data.

Leave the system alone, with your Disk 1 having one APFS Container that includes both macOS and macOS - Data.

That said, if your intent is to relocate your User folder to Disk2, you can do that in System Preferences:

1. First, in the Finder, create a new folder on Disk2 to become your new User folder (aka home folder)
2. Open System Preferences
3. Go to Users & Groups
4. Click the padlock and authenticate
5. Right (or control) click on your username and select "Advanced Options.."
6. Look for the line that says Home Directory
7. Click the "Choose..." button and point it to where you want your home folder to be.
8. Then copy the contents of your (old) User folder to the new location

... AND ... backup your data before you do this ... just in case something goes awry

Macintosh HD and Macintosh HD-Data are not partitions. They are volumes contained within the APFS bootable container; the container is the actual partition on disk. The two volumes are intimately related in ways that are not always what they appear to be. Catalina & APFS are much more complex (and different) than previous versions of macOS and many things we could do to the system in earlier versions of macOS can no longer be done. (As a simple example, I have had no success even getting symlinks to work on certain folders in ~/Library under Catalina.)

Macintosh HD is the sealed, read-only system volume that contains the macOS System & SIP-protected Apple apps.

Macintosh-Data contains user applications, various hidden system data and plus user data.

I would not recommend trying to remap the Macintosh-Data volume as a whole and I doubt it would work even if you tried. There is also risk you could corrupt the system by doing so.

If you are technically inclined, I recommend these articles for more information about Catalina:

• macOS Catalina Boot Volume Layout
• Working with APFS Volume Groups

stormenergy91 wrote:

Thanks for your suggestion, but in this way i can move only my user home folder.

My intent is to use a little SSD (32/64 GB) only for system and a bigger one for the Data partition, so i can install applications or add more users.

It sounds like you have either an iMac or a Mac Mini where you should be using a Fusion Drive setup which combines the SSD and HD into what appears as a single drive "Fusion Drive". This is why Apple includes the 32GB/64GB SSD to allow the large inexpensive storage of the slow hard drive with the fast SSD. Here is an Apple article with instructions for creating a Fusion Drive:

How to fix a split Fusion Drive - Apple Support

Besides you may run out of storage space trying to use just 32GB or even 64GB for even the base macOS system. You still need to keep at least 20GB of free storage space on your boot volume for the normal operation of macOS.

FYI, years ago I tried to do what you are attempting and I gave up when I realized macOS does not like to deviate from factory defaults. Things have only gotten more complicated as one of the other contributors have already mentioned. Yes, what you want to do is possible in theory if the boot volume has sufficient storage (I don't think yours does), but I would not advise it (even with just relocating the user folder). Some of us have learned the hard way and are trying to pass on our knowledge of past mistakes so you don't have to repeat our mistakes, however, it is your computer and you can do as you want with it.

When you succeed, please let us know.

I'm sure you are going to be doing some Terminal style command line modifications to the read-only volume from either Recovery mode or Single User mode, so I suggest you be prepared for this. If you use FileVault, you may need the FileVault encryption recovery key to access the volumes from Recovery or Single User mode (not sure about that, as I have not actually tried anything like what you are about to do).

And take Notes, so when you explain this you do not forget some small detail that might help someone else, as I'm sure you will start a trend.

I also strongly suggest you have backups (plural), because if anything goes wrong, you want to have your data safe. I suggest at least 2 backups, using 2 different external drives, using 2 different backup utilities to safe guard against bugs in the backup utilities and a failure in either of the backup drives. Then at least put the drives in separate parts of the house while you experiment so no single household accident will get both drives.

Or even better, if you have a 2nd system you can experiment on that does not have any of your real data on it, that would be better.

Some further reading:

• macOS Catalina Boot Volume Layout revised for 10.15 release

BTW, I just realized that I missed a step in the above instructions about relocating your user home folder.

After step #7 above you have to restart your Mac for the change to take effect. Sorry.