I am in the process of building a portable server for a friend. The plan is to have 

  • multiple Raspberry Pis
  • rugged, portable enclosure
  • fast storage
  • active cooling

I am going to document the build in this, and a couple more future blog posts

You can find the evolving BoM here. There are 2 options that I am trying to document - one with battery backup for data, and one without.

Microcontroller

A cheap ATTiny will be responsible for

  • power button and safe shutdown
  • I2C master for communication between the Pis
  • and most importantly - for fan control

Active cooling & Power

Given that this is going to be a portable server rig, I decided on using an active cooling solution as part of the case instead of relying on environmental conditions. I am using a 120mm fan with a standard 4 pin connector w/ PWM for speed control. This has some concerns that I am still working around - for example this will run on 12V. Nothing else on my system works on that voltage - RPi, PoE, microcontroller.

I decided to use PoE to power the Raspberry Pis as that would make reduce cable clutter. This complicates things on the cooling front - as there's already a fan on the official RPi foundation PoE HAT. 

Storage

I am using Crucial SSDs with a USB-SATA converter w/ UASP support. USB Attached SCSI Protocol is something that will give you faster I/O on the disk which costs practically the same. I intend to use the USB3 ports on the Pi4 for storage so this will most definitely matter.

Enclosure

I am thinking of using a design similar to the Mac Pro (trash can version). So the Pi4 will be vertical with the fan positioned at the bottom.

 

Conclusion

I am super excited for this as I think there's going to be a lot of portable server builds in my life and I'd like to set a great foundation for them :D

Let me know if you have any more ideas that I should incorporate in this! 

For example I am hoping to have a small OLED screen that I drive over I2C that shows the system status and some stats.