that's on me (author); I tried to cut the content down to a manageable post size that covered some interesting stuff - but probably dropped the connective tissue in the process. We'll keep this in mind for next time.

We run a thin base OS on the boxes and then VMs on top which we consider more ephemeral. The frequency of needing to update that base OS is v. low.

I think there's a case for building a custom PXE booted RAMdisk image to replace the install though; something like what Equinix Metal (formerly Packet) do with Tinkerbell (https://github.com/tinkerbell); they call it an OS Install Environment, but the idea is a small lightweight linux install agent that can DD a golden image onto the disk (vs. an install each time).

Maybe it needs to have more complex logic/detection and we need something more complex down the road. But it's like easy and cheap OCR for now.

what was kinda funnier was that I tried to get Claude to generate its own Go client code to upload the image and run the prompt; it totally totally hallucinated on that part :).

We're lucky to have a few great distributors/manufacturers who help us pick the right gear. But we learnt a lot.

We've found a lot of value in getting a broker in to source our transit though.

My personal (and potentially misguided) hot take is that most of the baremetal world is stuck in the early 2000's, and the only companies doing anything interesting here the likes of AWS,Google and Meta. So the only way to innovate is to stumble around, escape the norms and experiment.

When we started, we didn't have much of an idea about what the rack needs to look like. So we chose a combination of things we thought we could pull this off. We're mostly software and systems folks, and there's a dearth of information out there on what to do. Vendors tend to gravitate towards selling BGP+EVPN+VXLAN or whatever "enterprise" reference designs; so we kinda YOLO'ed the Gen 1. We decided to spend extra money if we could get to a working setup sooner. When the clock is in cloud spend, there's uh... lots of opportunity cost :D.

A lot of the chipset and switch choices were bets and we had to pick and choose what we gambled on - and what we could get our hands on. The main bets this round were eBGP to the hosts with BGP unnumbered, SONiC switches - this lets us do a lot of networking with our existing IPv6/Wireguard/eBPF overlay and a debian based switch OS + FRR (so fewer things to learn). And ofc. figuring out how to operationalise the install process and get stuff running on the hardware as soon as possible.

Now we've got a working design, we'll start iterating a bit more on the hardware choice and network design. I'd love for us to write about it when we get through it. Plus I think we owe the internet a rant on networking in general.

Edit: Also we don't use UniFi Pro / Uniquity gear anywhere?

Timeline wise; - we decided to go for it and spend the $$$ in Oct '23 - Convos/planning started ~ Jan '24 - Picked the vendors we wanted by ~ Feb/Mar '24 - Lead-times, etc... meant everything was ready for us to go fit the first gear by mostly ourselves at the start of May (that's the 5mo) - We did the "proper" re-install around June, followed closely by the second site in ~ Sep, around when we started letting our users on it as a open beta - Sep-Dec we just doubled down on refining software/automation and process while building out successive installs

Lead times can be mind numbing. We have certain switches from Arista that have a 3-6 mo leadtime. Servers are build to order, so again 2+ months depending on stock. And obv. holidays mean a lot of stuff shuts down around December.

Sometimes you can swap stuff around to get better lead-times, but then the operational complexity explodes because you have this slightly different component at this one site.

I used to be a EEE, and I thought supply chain there was bad. But with DCs I think it's sometimes worse because you don't directly control some parts of your BoM/supply chain (especially with build-to-order servers).

Re: Live Migration We're working on adding Live Migration support to our orchestrator atm. We aim to have it running this quarter. That'll makes things super seamless.

Re: kernels We've already seen some perf improvements somewhere between 6.0 and 6.5 (I forget the exact reason/version) - but it was some fix specific to the Sapphire Rapids cpus we had. But I wish we had more time to science on it, it's really fun playing with all the knobs and benchmarking stuff. Some of the telemetry on the new CPUs is also crazy - there's stuff like Intel PCM that can pull super fine-grained telemetry direct from the CPU/chipset https://github.com/intel/pcm. Only used it to confirm that we got NUMA affinity right so far - nothing crazy.

I'm going to save this for when I'm asked to cut the three paras on power circuit types.

Re: standardising layout at the rack level; we do now! we only figured this out after site #2. It makes everything so much easier to verify. And yeah, validation is hard - manually doing it thus far; want to play around with scraping LLDP data but our switch software stack has a bug :/. It's an evolving process, the more we work with different contractors, the more edge cases we unearth and account for. The biggest improvement is that we have built a internal DCIM that templates a rack design and exports a interactive "cabling explorer" for the site techs - including detailed annotated diagrams of equipment showing port names, etc... The screenshot of the elevation is a screenshot of part of that tool.

> What does your metal->boot stack look like?

We've hacked together something on top of https://github.com/danderson/netboot/tree/main/pixiecore that serves a debian netboot + preseed file. We have some custom temporal workers to connect to Redfish APIs on the BMCs to puppeteer the contraption. Then a custom host agent to provision QEMU VMs and advertise assigned IPs via BGP (using FRR) from the host.

Re: new DCs for failure scenarios, yeah we've already blown breakers etc... testing stuff (that's how we figured out our phase balancing was off). Went in with a thermal camera on another. A site in AMS is coming up next week and the goal for that is to see how far we can push a fully loaded switch fabric.

The host runs a custom daemon that programs FRR (an OSS routing stack), so that it advertises addresses assigned to a VM to the rest of the cluster via BGP. So zero config of network switches, etc... required after initial setup.

We'll blog about this system at some point in the coming months.