Learning never ends. This is especially true with computers and the near-daily changes the advance of technology brings.
I’m no longer so keep to be on the bleeding edge, but I also don’t want to find myself trailing. I’ve decided to retire my beloved Mac mini from its media server duties. With that in mind, I will shift that responsibility to my NAS. I already have the NAS and it’s already running so removing the Mac mini will save electricity. Saving electricity is good!
I didn’t limit myself to just that task. No, I had to go fooling with the drives in the NAS because I’m so damn particular about how my technology is configured. The positive aspect to this is that I learn more, especially if something goes wrong. The negative is things are far more likely to go wrong. In this instance, the negative can be nearly summed up by this notification from the NAS itself:

As you can imagine, this is never a good thing to see. I was relieved that I had all of the data backed up. However, I didn’t look forward to restoring all 10 TB of it! Ugh.
So how did I screw it up? The room with my computer is on the ground floor while the NAS is in the basement, one level below. When I checked my computer, it reported that the rebuild triggered by the drive I had moved would be finished in ten minutes. I went downstairs. While I can’t remember what I was doing, at least thirty minutes had passed when I was ready to pull another drive. Why would I go back upstairs to check if the operation was complete when triple the estimated time has passed? So, I thought it was safe to pull another drive I wanted to move. In my haste, I didn’t read thoroughly. I did not notice the rebuild was only the first step of three. Of course, all three steps had not finished. When I went back to my computer to configure the change, I was presented with the unwelcome message above.
What do you do when up make a procedural mistake? You try to undo the step that caused the problem! So I put the drive back where it was, not expecting a reprieve, but one must try. To my surprised, the NAS reported that it was now in read-only mode. It was trying to repair what I had done. Hours later it informed me:

Alleluia! Praise to the good favour of the computer gods! I was wary of the data of a repaired volume, but did some checking and everything looked good. I still have the backup just in case I discover isolated data damage in the future but things are looking good now.
The lesson? Check more than you think you need to check. Assumptions are bad!
Lesson learned, I continued onward, installing a media server app on the NAS, but that’s a story for another time. Happily, it doesn’t involve data loss. Not really.