This is the technical hardware specification for this guide.
You will need:
At least 3 computers that exceed minimum requirements for k3s, be they pis, NUCs, old computers, etc. They all need basic power and networking capabilities.
Ideally 6 TB of hard drive space, in three, 2 TB disks (as of Dec 2022), preferably in SSD form. One 2 TB drive per host. In fact, Longhorn recommends against spinning disks. Yes, if you want to sync the entire blockchain, 2 TB drives are required to use Longhorn because of the way snapshots and replication works. That said, reducing volume size is now a merged Longhorn feature, but we still recommend 2 TB for the purposes of giving longhorn extra flexibility as it moves volumes around hosts. Exception: We don't necessarily need to keep the full blockchain on every host, we can, after all, use pruned bitcoin instances, so if you want to use pruned instances (or if circumstances dictate it) you will have to design Layer 3 accordingly. More on this in Layer 3.Raspberry Pi Storage
Raspberry Pis This took us months of testing and returning hard drives till we found one. The only 2 TB drive that reliably fit the requirements was Samsung T5 2 TB portable SSD. In fact, it may be the only non-powered 2 TB SSD drive that works with RPis. Some considerations when choosing an SSD that went into finding the Samsung SSD:
- The RPi 4b 8gb can only deliver about 1.2A of power over ALL USB ports. Many SSDs require 1A or more. And some will accelerate performance periodically and consume 2-3A (like NVMe). Under such conditions, the SSD will simply stop working briefly, fail, or restart the Pi, and this is obviously problematic.
- For most drives, the more TBs the more amps needed. As such, before choosing an SSD drive, you will need to decide if you want to power the drive via a USB hub or not. If not, the options for a 2 TB SSD drive dramatically decrease. As of Feb 2022, the Samsung T5 2 TB portable SSD consumes .5A, is slow (as far as SSDs go), but fits the bill and has been confirmed by multiple sources to work seamlessly with RPis, to which we will add our name.
- If you are using a USB hub, make sure that the hub does not also supply power to the pi as this will absolutely cause problems.
NUCs If you are purchasing for the first time, we recommend buying "bare-bones" versions and then purchasing an additional 2 TB NVMe drive (if the NUC supports M.2, of course). Many NUCs will also support 2 TB SATA and there is always external options as well which many newer NUCs can support with thunderbolt / USB-C ports, choose according to your own budget and needs, much more things work than not in comparison to pi peripherals as NUCs are far more extensible.
Control/local computer to operate on the node (if you have a cluster of 3 computers, this is your 4th computer). It does not need any high performance stats or space, it merely needs to be able to run the software in Software Requirements and connect to the cluster hosts via ssh.
Network router with internet access. Preferably, you will use a dedicated pfSense box. The security model for this HAB node is largely predicated on a lot of pfSense features. For instance, keeping the node behind a dedicated firewall.
An SD card > 8 GB and/or a USB flash drive > 8 GB for flashing images. And if you have one for each host, all the better.
If you are not exclusively setting up raspberry pis you will need a keyboard & external monitor (and you shouldn't exclusively set up Raspberry Pis).