share Data partition/volume with Big Sur?

[edjusted]

I'm on a M1 MacBook Air with Big Sur. I'd like to install the Monterey public beta on a new partition/volume, and have it share my existing Big Sur data volume so I can boot off of either OS's to get a feel for the difference.

I know it may not be a good idea, but is it possible?

 

[gilby101]

but is it possible?

You could:

• Make sure your existing backup is good and you know how to recover everything in the event of disaster (see later).
• Create a new partition/container (not volume) for the Monterey install.
• The install will create both the read-only and data volumes for Montery.
• The Monterey data volume would have a new username and directory structure.
• Install a few test applications on the new Monterey data volume.

From Monterey:

• You would be able (subject to file permissions) to read/write your documents, pictures, etc. on the BS data volume.
• But don't let Monetary use your Photos, etc. libraries on the BS volume.
• Don't let Monterey use your BS Time Machine.

If/when you screw up, recover from your BS backup.

Recommended way: Use an external SSD for playing with Monterey and don't let it do anything to your BS disk or backup. To do this you will need to learn how to boot from an external disk. Even then you need to be aware that a Monterey install all make changes to the system disk.