- metadata raid1 with data raid5. If you currently have metadata raid5 'btrfs balance start -mconvert=raid1 <mp>' will online convert metadata from raid5 to raid1.
- raid10 with a device failure, you might think you have to wait a day or two for a device replacement, but in fact you can do `btrfs device remove missing <mp>` and the data on the missing device is replicated into the free space of remaining devices along with an online shrink, and the whole operation is COW and atomic per block group.
- raid10 with a device failure, you might think you have to wait a day or two for a device replacement, but in fact you can do `btrfs device remove missing <mp>` and the data on the missing device is replicated into the free space of remaining devices along with an online shrink, and the whole operation is COW and atomic per block group.