You can do that too, I just chose to use an external drive to keep things simple and compare apples to apples in terms of NVMe performance (part of my reason fo

You can do that too, I just chose to use an external drive to keep things simple and compare apples to apples in terms of NVMe performance (part of my reason for installing TrueNAS was to compare its performance to ADM built into the NAS, running with the same 12-drive storage layouts).