@JonathanM thank you for the link. I'd already watched that video, and read through a few threads/Reddit topics to get an idea. Hence why I was still using the old terminology of "Cache yes". I've installed the SSD already and gone through some trial and error, only to screw things up, but resolve the issue with a nuke and pave method.
To install the SSD drive, I stopped the array, added the SSD a new Pool called "cache", and then started the array again. All was fine and dandy at this point. I then went to the "appdata" share to see that Unraid had automatically set the "appdata" share to use Primary = cache, Secondary = array. Perfect! However, I wanted to move everything from array to cache so that it would never use the array.
This is where things when awry.
I set the appdata share to Mover = Array=> Cache . Then I disabled the Docker service (Settings > Docker > Enable = no), then went to the Scheduler settings to manually invoke the mover. I thought this would move the files to the cache. It didn't. At this point I wasn't sure if it had failed, or this is not what the Mover was supposed to do. So I figured, easy enough, I'll just use cp to manually bring the files over from /mnt/user/appdata/* to /mnt/cache/appdata/*. That went swimmingly. Then I started up the Docker service again, and then the crap hit the fan. I got a "Docker service failed to start" error on teh Docker tab.
To keep a long story short, almost nothing I did could remmedy the "Docker service failed to start" error. What did fix the issue was to revert everything back to the pre-SSD cache state. So I backpedaled until the SSD was reformatted and then re-added to a cache pool. Docker works, containers load, everything is running from the Array (no cache).
Now I have the appdata configured to Primary = cache, Secondary = array. I'm leaving it as such, and I'm going to research more into how to move things to the cache. Right now the mover is doing nothing because the cache is barely 50GB full out of the 1TB limit. I am thinking that the mover may never need to be invoked because I doubt I'd ever go about say 500GB full on the cache drive because the container that uses the mose space is Plex, and even then I don't have a gigantic library so its metadata and databases should be relatively small (i.e. less than 200GB).
So am I correct in thinking that just leaving the appdata share to "Primary = cache, Secondary = array" is the equivalent of having all docker containers running strictly off the SSD? I know that only new files and folders will be run off the SSD, but I assume that in the background Unraid is silently moving files over to the cache drive?