The copy process, the backup process, of the storage device which I shall use to back up a another OS to, will free up the device to install illumos on, has just passed it's twenty and a half hour mark.
Since the process is so extremely slow, using my SBC to execute this task is perfect because the Raspberry Pi5 uses very little power.
At this rate I will have the backup completed in about 5 hours.
Note:
Back-up storage is allowed to be slow. Many decades ago, way in the beginning, tape storage was also extremely slow. In the days of the Commodore 64 the datasette was an annoyance for many, since it was extremely slow, however it was reliable given the fact that you used proper tapes.