Since Kernel version 5.15 BTRFS is using dup for metadata on a Single disk profile. But when create a Single disk in OMV 6.3.2 it's create a FS with -d single and -m single. I thing it would be better to change -m to dup instead of single. ([HowTo] Convert BTRFS profile of Metadata "Single" to "DUP" (Duplicate of metadata is more safe than single) - Contributions / Tutorials - Manjaro Linux Forum)
Other question: Would it in the future be possible to change the profile from Single to RAID1 when adding a extra disk in the webui?
Just as simple:
Code
btrfs device add /disk /mount
btrfs balance start -dconvert=raid1 -mconvert=raid1 /mount