Ceph's BlueStore has talked direct to block devices, no filesystem in between, since 2017. https://ceph.com/community/new-luminous-bluestore/ https://ceph.com/

Ceph's BlueStore has talked direct to block devices, no filesystem in between, since 2017. https://ceph.com/community/new-luminous-bluestore/ https://ceph.com/community/new-luminous-bluestore/ [Disclaimer: ex-Ceph employee, from before BlueStore]