Areca 1280ml RAID6 volume set failed
Solution 1:
I think Option 1. is your best.
Take 12x new HDDs, 1x new RAID controller Try to mirror (dd if= of=) old disks to the new ones 1:1 using any linux box. Build a new server using the 1x new RAID controller plus the 12x new HDDs
Try to rebuild the array in the new server. Success? Great. Stop.
Rebuild failed? Mirror the old disks to new ones again, try Option i+1