When and why to deprecate filesystems

I too would like to see v2/3 go the way of the Dodo, but I don't think we'll probably be able to drop them that easily. One of the problems there is that at least some pNFS layouts (e.g. flexfiles) can use NFSv3 as a transport protocol, and some folks (Hammerspace, for instance) can use v3 servers as pNFS DS's. They may be able to eventually use v4.1 instead, but that sort of transition will take time.

This is probably a good discussion for the upcoming NFS Bakeathon.