- Requires a custom kernel to run. Although most of these patches are probably floating around the kernel mailing list in some form or another.
- Requires Google's RPC and authentication system. (I guess GRPC is open source now, IDK if piper has switched, but you still need auth)
- Requires Google's group membership seefvice.
- Requires Google's storage engine. I don't remember if they have migrated to spanner yet but even then it would be using internal spanner APIs not the cloud ones.
There are probably also more less obvious ones but the point is that when Google writes software to run in Google production it is based on top if a mountain of infrastructure. I'm not sure the design of Piper is in any way novel enough to be worth it. I mean piper works and scales well but I don't think it is a fantastic VCS.
