question about Project Zipper: File backend

Dear Daniel and those familiar with Project Zipper, I am interested in File backend mentioned in the following email, which is part of Project Zipper. https://marc.info/?l=ceph-devel&m=155542425904339&w=2 Daniel, do you have any idea in mind about how it will be implemented? For example, what kind of file interface (e.g. POSIX, NFS) will RGW use to access the backend? I am interested in File backend because it might be useful if RGW could be backed by File backend such as NFS server instead of RADOS. I guess RADOS does not work well on some storage devices such as tape, but such devices can alternatively be accessed via file interface. In such a case, it might be useful if RGW could access the File backend and treat it as a different storage class from STANDARD. Sincerely, Ken Iizawa