I have a 4 unit Multi Family building, and I'm looking to utilize a new 2gbps fiber connection
I want to provide Internet to the entire building, and also use CAKE to reduce bufferbloat.
Energy consumption is important to me
I was looking at a NanoPi solution, but I'm open to X86 Solutions if that makes more sense?
Budget maybe 200-$300 for the main router. I'll probably get APs for each unit.
Let each family have their own internet uplink that is independent and not influenced from the other families.
The tenants really enjoy having WiFi included in their rent. Utilizing a single connection is also much cheaper than many independent connections hardware wise and support wise.
You're probably going to have spend considerably more than that, especially if you want more than 940mbps (since that means you'll need 2.5G or 10G switches). Lots of detail and even hardware recommendations in this thread.
An odroid H3(+) with the 4 port addon (6x2.5) using VLAns to the units would probably get the job done.
Without SQM, yes - with SQM, doubtful.
I also like a full service package.
How do you guarantee bandwidth of let's say minimum 200 Mbps down, 50 Mbps up per family under all load conditions for at least 98% of the time? For the paid service.
The hardware is the easy part in this scenario.
Pretty much x86, the question is which one... I would go for something with 4 ports and add a dumb-AP/switch to each unit.
Traffic shaping @ 1-2 Gbps is hard work so I guess you need something pretty recent to get processing power and acceptable energy consumption in one package...
You do not... it is not that commercial ISPs offer that kind of SLA... However assuming the actual provider of the 1-2 Gbps link actually delivers, than splitting it out on a way that each family gets a CIR of total capacity / 4 and a PIR of total capacity is totally viable...
The 'trick" is to tell the end customers what kind of service you offer, just because traditional ISPs tend to offer simple "up to X Mbps" type contracts does not mean that endusers will not accept other kind of contracts, no?
Heck, at 2Gbps for a mere 4 units, I would as end user be fine with per-internal IP fairness being used to avoid single computers hogging all capacity under contention (but still allowing individual computers to get as much capacity as "left-over").
I agree to most of your reply, sure.
I asked the OP to think about this so that he could search for answers so that his tenants will be satisfied for the paid service.
I know how it is when you have to live, work or learn in a fixed shared medium environment with no effective quality of service mechanism and over provisioning. Even more when conditions change and you need to have consistent minimums.
When all families only have common spare time usage and there is enough capacity at all times: fine. If not, people work or learn from home while others are heavy users it can get different. I would take this into account before buying hardware for this scenario.
However assuming the actual provider of the 1-2 Gbps link actually delivers, than splitting it out on a way that each family gets a CIR of total capacity / 4 and a PIR of total capacity is totally viable...
Wouldn't only the uplink need to be 2.5GbE, the rest 1GbE ?
The flats will be capped at 1GbE, but that should be fast enough for most.
This depends on what you want to deliver, a gross 1 Gbps per unit, or up to 2 Gbps to each unit?
In any case the router would need to have 2 Gbps LAN capacity (e.g. by having individual true interfaces for each unit or if using a switch having a >= 2 Gbps CPU-to-switch port).
You won't get 2gbit/unit unless you over book, you're over booking already at 1gbit.
Not all people are willing to spend the extra $$$ required for 2gbit (2.5GbE hw in reality) though out their units.
But I guess it's up to OP.
Yeah I was looking at a few mini PCs like a beelink, but I wasn't sure if I needed to go X86 route, or if they consume more power
I'm not going to advertise it guarantee minimum speeds. Just WiFi included.
Heck I'm living with 100mbps right now and I'm fine.
I just wanted to splurge to give everybody a good user experience, and I myself want the extra bandwidth.
Jein, if you simply tell your users that they will share a 2 Gbps line, you solved the more or less unavoidable over-booking issue (unavoidable as the internet is a "shared medium" so the question is only at what segment under-provisioning/over-booking is going to become visible). But even then, if you want each unit to reach up to 2 Gbps you need fast enough interfaces (or a fast-enough) switch.
Sure, but that is their decision, if you want to offer shared-up-to-2-Gbps you need to make sure that each unit can actually get that throughput, but that does not force anybody to switch to > 1 Gbps ethernet gears obviously. That said 2.5 Gbps ethernet is becoming more affordable so the $$$ might turn into $$ and later $ 
Yes, we fully agree there.
That is a nice and friendly sentiment!
How much can a Banana Pi BPI-R3 route? with cake? it might be an option.
An x86 option would be something in a SFF with a 2.5Gbps card and another quad gigabit port card (intel, used?), maybe? But it does consume some more power.
2 GBit/s with sqm, I wouldn't even think about anything below semi-modern core i3 performance.
Stumbled over this badboy today. This (or something similar than this) probably has everything you want but is a bit over your budget. But i also saw them $ 100 cheaper…
But for an 12th generation i3 i think this is a reasonable price.
I keep plugging these Supermicro boards, since I've had such a good experience with them. They come in all manner of configurations, so you can get dual SFP+ ports with Quad 1Gbe ports if that's what you're looking for.
They work seamlessly with Openwrt and are pretty power efficient for what they are. The built-in IPMI management stack is also quite useful. I've been using a variant of one of these boards since 2012. The first lasted for 6 years before I upgraded it to one with a higher core-count.
They're fanless, but I did add a small Noctua PWM fan on top of the CPU.
There is also one more possible option in this case - You may use the provider's device (if being provided) for NAT and limit the speed to 500Mbps at each AP. Playing a service provider won't go cheap. I doubt you are receiving constant symmetrical 2Gbps service as a home user. If you are going to deliver some reasonable service, you will need to know the committed data rate of the connection - e.g. you may need to go to a small business type service. There is some additional benefit - You can also order an additional public /30 or a /29 for the tenants. You may leave a running iPerf for some time and see what will happen over the home-grade circuit... From my point of view it's better each tenant to have its own Internet contract - and taking the responsibility. You can still include the payment as part of the rent. Otherwise, if something goes wrong, you are going to be held responsible by the authorities for their actions and you will need to prove (somehow) who done it.
Why wouldn't he, I've had the option to get 10/10gbit from my current ISP, for the last 5 years, or more.