In my case 2x 1TB SSD under Big Sur this led to a big problem:
SSD's were partitioned as follows:
- 2x64GB on disk 0 and 1
- 2x936GB on disk 0 and 1
Following this guide I:
- created a 128GB APFS 'system' disk from disk0s2 and disk 1s2 in container disk3
And:
- created a 1.8TB APFS 'data' disk from disk 0s4 and disk 1s4
Either APFS (test) volume created in the disk3 container failed on exactly 50% of disk usage (the physical boundary) with a disk full error. This problem does not occur in JHFS+ In all cases Disk Utility states all is OK