This page has the following note
https://wiki.selfhosted.show/tools/snapraid-btrfs/
Note that although there's no harm with using BTRFS for the SnapRAID parity, there isn't any benefit from doing so to use snapraid-btrfs. It is recommended to use ext4 for the SnapRAID parity.
From the SnapRAID FAQ:
ext4 OK if the disks are NOT bigger than 16 TB. The parity is stored in a single big file, and ext4 has a upper limit of 16 TB for file size.
Drives larger than 16TB have become quite common. It would be quite a nasty surprise running into this hard limit only after your parity file has reached such a massive size.
This page has the following note
https://wiki.selfhosted.show/tools/snapraid-btrfs/
From the SnapRAID FAQ:
Drives larger than 16TB have become quite common. It would be quite a nasty surprise running into this hard limit only after your parity file has reached such a massive size.