thanks for all the help @MAM59 and @JorgeB
Just to round things off...
The official suggestion from @MAM59 is that the unraid array should NOT be ZFS and should remain as XFS (or BTRFS if you're brave)
I will begin the arduous process or converting all my array disks back to XFS.
I have turbo write enabled, and in the Disk Settings, I have it set to reconstruct write
I will perform the following actions.
Remove 1 parity disk
Allocate the removed parity disk to the array as Disk 5 with XFS
Let parity sync complete
Evacuate ZFS Disk1 to XFS Disk5
Format Disk 1 to XFS
Continue the disk evacuation and format process until all array disks are back to XFS
Aside from this painfully long process is there anything else I should do or tune?
Am I missing anything?
Would there be a faster way for me to complete the process of moving all that data around and reformatting disks and moving the data back onto them?
Right now my transfer speeds have dropped to 15mb/s. This is going to be an extremely painful process....
905jay's post in ZFS Array transfers very slow was marked as the answer