The problem
It all started with a simple problem. I am a freelance software engineer, and I’ve got one hundred or so virtual machines running various server tasks for both my clients and myself. These run on a handful of physical servers attached to a fibre internet connection.
I’ve been running these for years and everything works well, so what’s the problem? They’re all second hand enterprise Xeon servers, and they use power. A lot of power. Electricity in the UK is expensive these days, and the power bill was starting to get silly.
Looking for a solution
When I started looking at what the VMs actually do, I realised quickly that although there were a lot of them, they didn’t individually need that much compute power. I wondered whether something as simple as a Raspberry Pi would do the job, and a few experiments proved that they would.
So, just buy a load of Raspberry Pi 4s and move all the servers over to those? I could have done that, but a couple of things stopped me.
Firstly, I wanted everything rack mounted. The servers they would be replacing are in a rack, and I wanted to keep it similarly neat. There are quite a few rack mount enclosures for Pi’s out there, but none that particularly grabbed my attention.
Secondly, I wanted some sort of centralised remote management. Every now and again you’ll need to power cycle a server. My rack lives in an attic and I’d rather not have to climb the ladder every time I need to do a hard reset. There didn’t seem to be any suitable hats to add to a Pi 4 to do this over a network.
Some kind of server based on a compute module seemed to be the obvious solution, but when I started looking around there was only really one blade server for the compute module, and it wasn’t available for me to buy. It also wasn’t as server-focused as I was looking for, with central management services.
If it isn’t available or doesn’t exist, then it’s time to DIY.
My background
My full time job is as a professional software developer, but I started my career as a network support engineer. I spent many years setting up and managing all sorts of servers for hundreds of different businesses, so I started this project with a clear idea of the kind of things that I wanted a server to be able to do.
Although I’m really a software guy, I’m also an electronics enthusiast. I’ve been tinkering with hardware for a long time and have gradually learned to make my own PCBs. Over the last few years I have built lots of different hardware projects for my own use. When I realised that there wasn’t exactly what I wanted ready to buy, making my own was the obvious next step.
Meet the PiRack
This is the server I ended up building:
- 2U rack mount case
- Slots for 10 blades
- ATX server power supply
- 2.4” LCD front panel display
- Remote management server
- 3 x 60mm case fans for cooling
Each blade has the following:
- Socket for Raspberry Pi Compute Module 4
- Front panel connectors:
- Gigabit Ethernet
- HDMI
- USB type A
- OLED status display
- M.2 NVMe socket supporting 2230 to 22110 drives
- Micro-SD slot for CM4 Lite
- PCF8563 real time clock with battery backup
- RP2040 for management of the blade
- Powered by the server backplane
There is more detailed information in the next blog posts about the design of the PiRack. It was built so that if it worked well it could be turned into a saleable product. I’ve been running it successfully for a while now, so it’s time to open it up to the world!
Open source
Although I am selling complete PiRack units, I am planning to open source the design and software. Lots of elements in it are built on open source code so I am happy to make this available too. These will be published once the first production units are ready later in December.
Pricing and availability
A small number of PiRacks will be available to buy by the end of December 2023. If there is enough demand then I will do a larger production run in January 2024.
The PiRack with 10 blades will be priced at $835/£675/€785. This doesn’t include any compute modules, which are available in quantity now from the usual Raspberry Pi retailers.
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Want to know more?
If you want to know more about how this was designed and built, I’ve got much more detail in these other blog posts: