Apple Raid of SoftRaid volume?
I have a Thunderbay 4 (thunderbolt connected) on a MacBook Air with Big Sur 11.1 and 6.0.1 b47.
I experimented with using SoftRaid to volumes on on the TB4 and asking Disk Utility ->File -> Raid Assistant to stripe them. I see a post from a few years ago indicating that someone had created JBOD and done this and had problems, and that at the time it was something that was expected to work.
Raid Assistant does not permit me to select volumes I formatted as APFS, but it does permit me to select volumes I formatted as HFS+.
However, when I try this, it gets part way through (creates container disks) and then fails at the point of creating the filesystems, saying that it cannot update the partition information. That kinda sort-of makes sense, as it is not dealing directly with drives.
Is this a supported operation?
Disk Utility does not understand SoftRAID disks. So "zero disk" before you try using a SoftRAID disk with Disk Utility. This is a bug going back to 10.2 and will probably never be fixed by Apple.
Sorry, I am not sure what you mean by "zero disk" in this context?
Disk Utility cannot manage SoftRAID formatted disks.
So in SoftRAID 'Zero disk', which will wipe the partition map from the drives, and Disk Utility will treat it like a brand new disk.