Last updated 11 March 2024
During 2019 Synology started using device tree and sata1, sata2 etc instead of sda, sdb etc, for new '20 series models with CPUs that Synology hadn't previously used.
For the current list of models that use sat1, sata2 etc see:
https://github.com/007revad/Synology_enable_M2_volume/wiki/Models-that-use-DeviceTree