Thanks for the link, ntrance.
So it took a bit of futzing (the new HD was pulled from a Windows box and I had to re-partition it with GParted before the HR20 seemed to even want to acknowledge it, though in retrospect it's possible that was unnecessary and I was just impatient with the HR20), but I got the drives set for the copy. (As in, each HD was pulled from the HR20 after doing the s/w reset, pulling the power cord just as the LEDs go out.) But when I started the xfsdump command as specified, it took a whopping 8 seconds to run. My original HD is not full, but it should certainly have taken longer than that. I was very, very careful to make sure I had the correct drives as "sda" and "sdb", with the partitions # 2 & 3 of each mounted as "fap" and "hr20" respectively - 100% confidence about that. I double and triple checked in the GParted window. But looking at the following command from the instructions:
That just looks backward to me. "fap" is the mounted original HD, and "hr20" is the mounted new HD. Isn't this attempting to dump the new and restore it to the old, which is the opposite of what's desired?
xfsdump -J - /mnt/hr20 | xfsrestore -J - /mnt/fap