The architecture does indeed come from the late 80s/early 90s, but I think it's more relevant today than ever. Separation of services is, in my opinion, essential to security. By putting the authentication service off in its own machine, you restrict the attacks that can be made on it; the auth server only talks over a highly restricted protocol. On a standalone Unix system, users log in to the same machine that stores the passwords. They're only a privilege escalation exploit away from getting the hashes of everyone's password, and these days privilege escalations are a dime a dozen.

When this scheme was designed, it was frankly a little bit nutty. The CPU, auth, and file servers would be VAX or Sun systems, costing tens of thousands of dollars, and the terminals would be either slightly cheaper Suns or IBM PC-compatibles costing thousands of dollars themselves. Today, you could probably cobble together a passable network for a few hundred dollars, assuming you use cheap Atom boards for everything except the CPU server (which is meant to be a beefy compute box, but let's be honest nothing in Plan 9 uses a lot of cycles). This makes the architecture more sensible than ever.

Like how functional programming came from the 80s or earlier?

That would make it an improvement over whatever else you are using which is most likely running on an architecture designed in the 60's and first implemented in the 70's.

>This architecture sounds old to me, as in things were built like that in the 80s or earlier but evolved past.

Actually most modern OSes in use are even older in their concepts.

Plan 9's concepts as described above have slowly creeped into Linux but not fully. So the architecture above was only experimental in the 80s/90s and is still nowhere available in the mainstream today.

So your concern is like saying "we've had macros and closures since the 70s" in a world that still uses Java/C#/etc.

Here is an excerpt from the about page, I don't know enough to argue for or against the architecture but this part caught my eye.

"those who believed in Harvey were thought to be insane, but eventually found not to be."

So they recognize that many will think it is an insane idea but are playing a long game to prove that to be incorrect.

================================

About the Name

So, why “Harvey”? Mostly because we liked it, but there are at least 3 other good reasons based on the origins of Plan 9 operating system:

Harvey is a movie, Plan 9 is a movie too. Harvey is a rabbit, Glenda is a bunny. Most importantly: in the movie, those who believed in Harvey were thought to be insane, but eventually found not to be.

https://harvey-os.org/about/

Why does the architecture's age matter? Things do not just magically stop working well. Why the obsession with novelty?

One nice thing about Plan9 is there is no concept of "root".

Plan9 "fixes" many of the flaws/deficiencies of the original UNIX, such as that one.

Whats cool about this Plan9 project compared to the original Plan9 is one does not need to use the Plan9 compiler to compile it. One can use gcc, clang or icc.

The idea does indeed come from the 80's, but things didn't evolve past them. The architecture of our current OSes was settled at the 60's and early 70's, and we never moved from it.

It is not clear why such things were never adopted. There were many licensing problems on the way, and a Microsoft monopoly pushing things into even older architectures than the competition. There were also failed modern projects, but there is little evidence to decide if it is a hard problem, greed people forced everybody into a worse path, or if it is something people do not want.

Having a file server that only stores files does not mean having only one file server.

A server is just a name; you can't infer the number of machines (physical or virtual) that are behind a name.