They are running brtrfs on top of DM. https://kb.synology.com/en-nz/DSM/tutorial/What_was_the_RAID_implementation_for_Btrfs_File_System_on_SynologyNAS https://k

They are running brtrfs on top of DM. https://kb.synology.com/en-nz/DSM/tutorial/What_was_the_RAID_implementation_for_Btrfs_File_System_on_SynologyNAS https://kb.synology.com/en-nz/DSM/tutorial/What_was_the_RAID...