MP 6,1 Monterey and Mojave on same volume?

[Oliver M]

I am running a Mac Pro 6,1 with internal Apple SSUBX 1TB SSD.

I would like to install macOS Monterey as the primary operating system and macOS Mojave as secondary. Both operating systems on the internal SSD on two different volumes of a container.
I understand that Monterey runs on APFS 2 and Mojave on APFS 1. Should I expect problems because of this?
Will the 2nd volume be reformatted as APFS 1 during install?

I definitely don't want to run one or the other operating system on an external drive, both should be on the internal.

I’d also like to avoid having to create two partitions.

 

[tsialex]

While this is something that in theory could work perfectly fine, when you implement in production it literally fails - Mojave APFS and Monterey APFS are essentially incompatible and very much hate each other.

You will have lot's of issues, the first one is Mojave nagging/warning all the that Monterey is incompatible and vice versa, the second one is that you will corrupt your disk overtime with data loss.

 

[Oliver M]

🙏🏻for the reply, ouch, thats too bad. I am no fan of partitioning as this may cause similar issues. So the only solution is (yet another) external drive then.

 

[DouglasCarroll]

While this is something that in theory could work perfectly fine, when you implement in production it literally fails - Mojave APFS and Monterey APFS are essentially incompatible and very much hate each other.

You will have lot's of issues, the first one is Mojave nagging/warning all the that Monterey is incompatible and vice versa, the second one is that you will corrupt your disk overtime with data loss.

What about Mojave and Catalina?

thanks!