Raspberry Pi server clusters

OK, lets construct an 8 board Pi Cluster.  On each Pi you install a 90 deg I/O port header.    Then design a interconnect board that these plug into.  The Pi's mount vertical to the horizontal interconnect board.  This board distributes  power/ground to the Pi's and also connects all the I/O ports together for what ever we want to use them for.  Such as broadcast communication.   Some I/O ports could drive  status LEDs for each board.

Each Ethernet port is connected to an 8 port Ethernet switch/router for communication.  S/D cards are available from the rear and the USB's are available from the front.   The 8th board connects to a video terminal and  keyboard/mouse/printer via a USB hub.    Video and keyboard/mouse is available from each board for trouble shooting.

Each Pi is separated by about 1" so the whole thing; Pi's, interconnect board, power supply and Ethernet switch fits inside a shoebox.   

Physically, I think I'd start by designing a pluggable module enclosure for the Pi, just to make life with large N less of a bother.  A good quality rear-facing connector will have to be chosen for the module, perhaps something from the DIN41612 line.  Then N identical inner module looms can be assembled, an extremely boring operation but once done, you'll never again have to touch the wiring.

I'd place the design on Thingiverse, naturally, and 3D print it on my own Shapercube if it's operational by then, or on a friend's printer if it's not.  (Or, your local hackerspace will be delighted to print it for you!)  RepRap-type 3D printing is ideal for this, since smooth surface finish is not required and you can iterate repeatedly at home and at very low cost until you have exactly what you want.

It is possible that the pluggable module will have to be substantially bigger than the Pi,  because the Pi's connectors come out in all directions and the module will have to accomodate the chosen connectors within its form factor.  Which Pi connections are brought out to the rear module connector needs to be decided based on two factors, first the core signaling issues (only those connections tolerant of poor impedance matching and significant crosstalk are likely to work well through a universal connector), and second the goals of the cluster builder.

A spectrum of designs is likely to emerge based on the goals for which a cluster is built.  I suspect that the most popular type of cluster module will need only power and Ethernet to be routed to each board, although of course every self-respecting geek will also require front-panel LEDs to be routed to the GPIO lines.

It should be mentioned that  we're discussing clustering Pi boards here because this is a Pi-oriented group, but the board's physical layout is poorly suited for building clusters, even for those applications where the board's capabilities are sufficient.  A better candidate for building clusters would be a board designed as a pluggable module from the start, such as Rhombus Tech's EOMA68 form factor module -- http://rhombus-tech.net/ .  Based on the very successful Allwinner A10 CPU (an ARM Cortex-A8) -- http://rhombus-tech.net/allwinner_a10/ -- and with an estimated BOM cost of $15, this would obviously be easier to employ as a cluster node directly.  Unfortunately it doesn't exist yet, so its better features are quite academic.   Keep an eye open on progress there though.

For now, we'll just have to work with the Rpi's connections coming out at all angles, as no other Linux board is available in the same price bracket.  If all you need to connect is power and Ethernet, it's very easily manageable anyway.

Morgaine.

Hey, everyone knows that Rpi isn't as powerful as conventional supercomputer, but there are some applications which can make use of this low computing power, things such as swarm robotics, 3d printer etc can take this job pretty well, instead of writing linear code you write parallel code, weather simulation is a big deal with Rpi, leave small miniaturized supercomputers built for stuff like biological analysis like Little Fe http://littlefe.net/ .Check the link. And also the LMU project done by scientist is just a demonstration that anything can be done with ARM.

I still need to do more research to come to a conclusion. Guess this will be my final year project with some parallel code running on it.

Allwinner A10 looks like a good material to me. If i need to do something good enough which is close to the Apple TV cluster done by LMU people. And your jargons are pretty tough to catch up..maybe because you are a pro. And yeah i checked the Thingiverse 3D Open Source printer. Does it run on parallel code? I highly doubt that. I think a linear code is enough, but in which language will you code, use Robot Os? Maybe i'm taking this thing too far..i need to think about the architecture of the cluster first and then think about coding later.

Kishore

http://www.nm.ifi.lmu.de/~kranzlm/vortraege/2011-10-06%20Stuttgart%20-%20HPC%20Forum%20-%20HPC%20and%20the%20AppleTV-Cluster.pdf

http://www.nm.ifi.lmu.de/projects/ATV2CLUSTER/atvcluster.pdf

These pdfs seem to be pretty useful..found 'em out by googling. Hope this atleast inspires me to start something which i always wanted to do.

That fits in well with my interest in introducing low-power sustainable computers into the network environment. The only difference is that I am working on plans for a low-power server using all SSDs. After I lauch my desktop which is still in beta sometime in the next few months, the server is next along with some investigation of mini-clustering. It would be interesting to compare stats later on in my project in terms of energy foot print and performance. Right now I'm working in the mini-itx format and looking at the mini (3.5") format for a follow-on. Another area to explore clustering in is VmWare envionments and even setting up mini SANs.

> "introducing low-power sustainable computers into the network environment"

I like your phrase a lot, Bob.

I'm pretty proud of the "sustainable" part considering I built a fully functional desktop PC from off-the-shelf parts. It has no moving parts other than the on/off switch, meets or exceeds all international standards for contect of toxins and green efficency, can be constructed with nothing more than a screw driver and only uses 33 watts of power at peak operation. The PC is 95% recyclable. I am looking forward to boards like RPi coming up in performance enough to drive a SSD and handle more memory which would allow it to drive more resource intensive OS's...(read Windows). As it is, RPi looks like a pretty good platform for running a VmWare image. I hope to experiment with that.

The "sustainable" word was one of the things that attracted me to RepRap 3D printing, because the project founder Adrian Bowyer mentioned that old extruded items could (in principle) be melted down and recycled into plastic filament ready for your next print.  He gave a very alluring example of when your child outgrows her sandals, you melt down the plastic, add a bit more filament, and print out a slightly larger pair ... with the added punch line that PLA polymer is biodegradable and can be made out of corn that you've grow in your back yard. 

Of course, reality is a lot different to principle, and extraction of pure ABS or PLA from old sandals would be difficult, not to mention that extruding filament to the required fine tolerance is not something that you can do at home (yet).  And I'm not into farming corn.  Still, the thought is there.

The real reason I'm mentioning 3D printing though is in answer to your building low-power sustainable computers, because 3D printing makes it so easy to build enclosures that evolve with your requirements.  My printer isn't completed yet, but once it is, it'll be near the top of my list of applications to create pluggable modules for various things, including microcontrollers and Raspberry Pi cluster nodes, as I discussed here earlier.

The low power consumption of ARM and the ability to construct plastic enclosures to suit your specific needs seem to go together rather well, and provides ample opportunity to reuse parts from obsoleted or failed equipment.

Morgaine.

Hooray,  objective measurements are starting to appear as more people receive their Pi boards:

• http://candgsoc.host56.com/2012/04/quality-time-with-a-raspberry-pi/

It's very important to match what the board can offer against the specific requirements of your application, otherwise it can lead to disappointment.  Also, it's crucial not to make a one-dimensional analysis when multiple factors come into play, as cand's article highlights --->  the Pi's Ethernet performance can approach the full bandwidth of the line, but only at a huge CPU cost.

First indications then suggest that networked applications of Pi are likely to be most successful when the network use is occasional and when not much else has to be executed concurrently with the communications.

This will need a lot more careful analysis so that we know exactly where the bottlenecks are.  Some of them are quite likely to be remedied by kernel config improvements or with better drivers, but one has to know the detailed cause of a problem before one can tackle it.

Morgaine.