I have 12 - 12TB disks in my Unraid server. I want to remove 6 of the 12 drives without data loss. What are my options? 

Do the 6 disks you want to remove have data on them?

Yes, each disk seems to have a few files, I want to remove disks 10, 9, 8, 7, 6, & 5

Is there a way to migrate the very small amount of data off the disks and then remove them? If I have to I will preform a full back up but that takes a few days even over 10Gb

 

Once removed I will create a ZFS2 volume, move all the data to the new volume and physically remove the original 6 12TB disks. 

You could use the plugin unBALANCE to move your files.

 

Select the source, the destination and run it.