I'm sure you're trying to help and appreciate the reply...I know a fair bit about what I'm doing but this ended up being a lot of things just happening to occur at once. Upon looking at my original write-up here (quickly done while leaving work) I realize I didn't properly indicate what happened in the correct order. It's pretty bad off, in fact...my apologies. I've tried many things and the exact order of them is beginning to blur in my head with all of the rebuild/pre-clear/drive-shipping time. The things that I did all took place for a reason and the way I wrote it up does sound pretty bad, you're right. Let me try to clarify.
Absolutely understood. My parity and all other drives were happily working the entire time.
The drive I added originally was pre-cleared and just, I mean JUST added when I realized the other one had failed, hence the reason I didn't just use the new drive as a replacement and then bump up the storage with a different drive later after all was cool. I could've created a new disk config but as I had never done that without a full OS reinstall I wasn't sure what else that would be wiped config-wise, especially with one already failed drive, so I decided against messing around too much and just ordered an additional replacement drive right away.
Totally. The reason I copied the data off of the simulated disk is because I had just added a larger, empty drive to the array and it would be two days before my replacement arrived. As you said, data is king here so once it was copied I felt better. That's all. Replacement drive was added in place of the failed disk two days later and all was right in the world of drives.
Yes, I went from the latest beta (Beta 15) to RC2 directly in the interest of troubleshooting my docker issue. I had run out of ideas on getting the docker issue resolved with the .img and drive scrubs, .img rebuild, container re-adds, and permissions checking, I had my data copied off onto the new array drive so I didn't care too much about a drive rebuild, and the failed drive's replacement was pre-clearing (83 hours) in another computer so I could reboot while troubleshooting docker without losing my progress. At that point I figured hey, what the heck...might as well upgrade in case that fixes it. The risk really was minimal even though my original write-up sounds pretty bad. Sorry about that.
As I said in my original post, I don't believe what's going on is related to the drives at all as they all acted, restored, parity-sync'd, and expanded my array as intended...I only added the details in case it would help get to the bottom of my issue. I expect either the Docker issue is a result of the several reboots, something along the lines of that BTRFS bug (not likely as I've already switched the cache drive to XFS), or something to do with the initial drive failure and general unhappiness.
Hopefully I've redeemed myself a bit with the clarification. Thank you again for any suggestions you may have.