BTRFS driver description is ambiguous

I read here: that “btrfs requires a dedicated block storage device such as a physical disk. This block device must be formatted for Btrfs and mounted into /var/lib/docker/.”

I already have two SSDs in RAID1 for the op system which have 100GB free space. Is it possible to use that free space instead of buying a new disk again?

(note that the forum behaves very strange on Firefox, the topic title is white I can’t see what I wrote there and the tags selector does not lose focus)

I read the whole section in the docs, it does not appear to require a dedicated device for docker, just something formatted with btrfs. I’ll try it out tomorrow.