Richard Downer presents a thought experiment about building a cloud computing cluster using Raspberry Pis instead of virtualized PCs. He summarizes that the Raspberry Pi's performance is comparable to an EC2 t1.micro instance, and that a 32-core Raspberry Pi cluster's costs are comparable to a powerful Dell PC. However, there are some technical issues to overcome regarding provisioning and booting user images on the Raspberry Pis. While not a fully feasible solution today, the idea is not completely unrealistic and merits further exploration.

1. Raspberry Pi Cloud:
a thought experiment
Richard Downer
Twitter: @FrontierTown
GitHub: richardcloudsoft & rdowner
Principal Engineer @ Cloudsoft Corporation
This presentation is my own work and may not represent the views of my employer

2. What is a Raspberry Pi?
“The Raspberry Pi is a creditcard sized computer that plugs
into your TV and a keyboard.
It’s a capable little PC which
can be used for many of the
things that your desktop PC
does, like spreadsheets, wordprocessing and games. It also
plays high-definition video. We
want to see it being used by
kids all over the world to learn
programming.”
(http://www.raspberrypi.org/faqs)

3. In more detail
• ARM-based SoC with plenty of I/O
• 700 MHz ARM11 core
• 256 / 512 MB RAM
• Low cost - $25 / $35

4. The thought experiment
• Could you build a cloud using a cluster of
Raspberry Pis, instead of virtualized PCs?
• Is the performance comparable?
• Is the cost comparable?
• Is it technically possible?

5. Performance
• Amazon EC2 offers “t1.micro” instances
EC2 t1.micro
Raspberry Pi
Processor – normal
Undisclosed
700 MHz single core
Processor – spiked
2 ECU single core
(ECU approx equivalent to
2x 1GHz 2007 era Xeon)
700 MHz single core
Memory
0.615 GB
0.5 GB
• Conclusion: slightly inferior

6. Costs
• Model B Raspberry Pi is $35
• Scientific researcher built a 32-core cluster
using Raspberry Pis for $1967.21

7. Costs
• Dell PowerEdge R520 for $2759
– List price – discounts almost certainly available
• Intel® Xeon® E5-2440 – 6-cores @ 2.4GHz
• 16GB memory, 500GB hard drive
• Compared to the Raspberry Pi cluster:
– Same RAM
– Equivalent to a 16GB SD card in each Pi
– 6x 2.4 GHz = 14.4, versus 32x 0.7 GHz= 22.4

8. Technical issues
• There’s no virtualization, no hypervisor, no
PXE boot – just an SD-card based bootloader
• How could we provision the user’s required
image automatically?

9. Technical issues
•
•
•
•
•
A “bootstrap” OS
Starts on Pi reboot
Erases all data on the user partition
Clones the OS image from network storage
Re-boots into the user’s OS

10. Summary
• Performance – comparable with an EC2
t1.micro
• Cost – 32-core cluster comparable with a
heavy-duty PC
• Technical – some issues but it is feasible

11. Conclusion
• It’s not a completely ridiculous idea!
• But this is only a thought experiment…
• Not considered:
– Physical rack mounting
– Network switch port demands
– Thermal requirements
– Power consumption and distribution
– Reliability and lifetime of a Raspberry Pi

12. References
• Raspberry Pi official website:
http://www.raspberrypi.org/
• US boffin builds 32-way Raspberry Pi cluster:
http://www.theregister.co.uk/2013/05/20/32_wa
y_raspebrry_pi_cluster/
• Dell PowerEdge R520
http://www.dell.com/us/business/p/poweredger520/fs
• Intel® Xeon® Processor E5-2440:
http://ark.intel.com/products/64612/

13. Addendum
• The University of Glasgow’s
Raspberry Pi Project:
http://raspberrypicloud.wordpress.com/
(thanks to Matthew Broadbent for bringing this project to my attention)