Running between two external drives on another machine
 

Our Mac Pro 2008 is in retirement as a Linux powerhouse. It boots from a 2.5" SSD on a PCIE adapter card, and with 52GB RAM, an Nvidia card and a ZFS array that uses all four SATA bays, it is doing fine.

I still have a MacOS High Sierra APFS boot drive for the Mac Pro, a 3.5" spinning hard drive.

I'd like to clone the MacOS 3.5" drive to a 2.5" SSD, then temporarily mount that on the PCIE adapter card when/if I ever need to boot MacOS again.

It would be most convenient to clone from the 3.5" MacOS HD to the 2.5" SD if they are both in external USB cases connected to a Mac Mini 2018 running Mojave.

Can I run SuperDuper! on the Mac Mini to accomplish this?

Just to add: I'd like to keep the ZFS array intact for now not just for the convenience but also because learning how to access the ZFS array from MacOS is a part of the exercise.

That should work, assuming the mini is running the same OS version or later.

I was able to cobble something together using some
spare SATA ports on the motherboard and then run SD! between both
drives on the Mac Pro. For now, it is working (booting) from the SSD,
even if it does not look very elegant.