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Assigning a disk to a slot that didn't have anything assigned to it the last time the array was started, is exactly what triggers a rebuild. In fact, what you did is basically the same as the "rebuild on top" instructions:
https://docs.unraid.net/unraid-os/manual/storage-management/#rebuilding-a-drive-onto-itself
 
Emulated disk5 still unmountable. Have you tried check filesystem on disk5 since you upgraded?
 
 
 

Your disk assignments, passwords, all settings from the webUI, are on your flash drive, so something must have happened to break that, probably corruption.
 
Format your original flash drive, then install your most recent flash backup on that same flash drive. If you think there is any chance that you have made disk assignment changes since that backup was taken, edit config/disk.cfg on the flash drive to disable autostart so you can check the disk assignments before starting the array.

Probably not a unique GUID, you'll have to try another. 

Do you mean you have reserved the IP in your router, or do you mean you have set an IP in Unraid?
 
Attach diagnostics to your NEXT post in this thread.

Your syslog is full of the same errors. Reboot and post new diagnostics.

Is this from another computer on your network? Does it also happen if you boot GUI and try to access using attached keyboard and monitor?

Can you see if your router has given it an IP address? Maybe it is working headless and just the video output isn't for some reason? 

Have you checked all ports, plugs, cables on all switches and routers involved? 1G degrades to 100M if one wire isn't working.

Does look like a disk problem on disk 6. You might run an extended SMART self-test on it.
 
But if you want to replace with a larger disk, that seems like a good idea also, since you need more capacity.
 
Do any of your other disks have SMART warnings ( 👎 ) on the Dashboard page?

cache is full

This is less than ideal, because normally I would ask for you to post the output of this command:
xfs_repair -nv /dev/sdg1 It may not all fit on one screen for you to photograph.

Mirror counts as protected, but if you have some files for the share on unprotected storage, it won't be green.
 
You can see how much of each disk or pool is used by each share by clicking Compute... for the share on the User Shares page.

Diagnostics shows 6 slots for a pool named cache with nothing assigned to any of them. All the connected disks are part of the array, except for a single 2TB nvme which is unassigned. If there were ever any other attached drives they didn't show up for the reboot.

If it hasn't finished after a few minutes eject and see if it works. If not try 
 
https://docs.unraid.net/unraid-os/getting-started/manual-install-method/

I assume you mean from the Unraid webUI?
 
Then you won't have the functionality you are asking about. Simple as that.
 
 

If writing to an array with parity, they can't be independent even if the destination is different disks, because parity is realtime and has to be updated for each.

Just let it finish disk5 and if that goes well we can do disk3.

Yes, New Config. But if there were any writes to the emulated disks, those writes would be lost if you don't rebuild the data. Sounds like that might be your best solution anyway, at least rebuilding parity wouldn't write to any disks except parity.
 
In any case, probably better to try to identify the problem before trying to fix it.
 
Attach Diagnostics to your NEXT post in this thread.

ssdpool is corrupt and has gone readonly, and that corruption caused docker.img corruption.
 
Disable Docker in Settings until you get this resolved.
 
The usual advice is to backup pool contents, reformat, restore.
 
You will have to recreate docker.img and reinstall containers from Previous Apps.
 
Have you done memtest lately?

I understand why all of the data is going to the first disk, because it hasn't hit highwater yet, but will soon. What I don't understand is why any files are on disk3.
 
What is the purpose of this user share?
y-----e shareUseCache="only" # Share exists on cache, disk3  

See if it runs without your config for a while maybe there is some corruption with those files you are restoring.

If you haven't changed any disk assignments since then.

You want to delete System, not system. Unraid is not confused. It is showing you the correct names. Your screenshot is showing the contents of System, the file you want to delete.
 
If you notice, the dates on the 2 different docker.img in the 2 different shares (system and System) are different. The System share is older and not being used.
 
Also, it won't let you delete the file in system because it is being used.

Looks like more might have been added to the lost+found on the emulated disk1.
 
If you rebuild disk1, the result will be exactly what the emulated disk shows. If you rebuild to a new disk and keep the original as is, you will have both to work with to recover files.
 
The linux "file" command can help determine the type of data a particular file might contain.