Hi All, I found this document from Feb 2019, and after some amazing help from Craig and others I came up with this: Proposed road map for an installation of a system disk and two Data disks set up as a RAID1 array 1Tb SSD and 2 x 2Tb SATA HDDs Using Gparted partition the SSD 512MB EFI Partition dev/sda1 formatted FAT32 primary (boot?) 8 Gb SWAP rest of the disk _*/*__dev/_sda3primary formatted btrfs Partition the first HDD /dev/sdb1primary formatted btrfs (Disk has data now so leave this alone) Second HDD same size leave completely blank (also leave this alone) Remove the gparted disk and insert the Ubuntu Server disk commence the install Install the system and add the GUI using tasksel After the system is installed run the- /device add/ - process and the /balance/ commands two lines in the terminal - my question is will these commands remain the same? sudo btrfs device add -f /dev/sdc1 /data sudo btrfs balance start -dconvert=raid1 -mconvert=raid1 /data You can do this after the system is installed, or from a root shell while booted on gparted. It doesn't matter either way, although it's probably better/easier to do it from gparted (there'll only be the one /data fs for the ubuntu installer to detect so you won't end up with /data0 and /data1 again) craig Many thanks Andrew Greig