Raspberry PI 2 Cluster Case pt2

This is the second post of a series about Raspberry PI 2 BigData cluster case.

  1. Raspberry PI 2 Cluster Case pt1
  2. Raspberry PI 2 Cluster Case pt2
  3. Raspberry PI 2 Cluster Assembly Tutorial
  4. Build Hadoop Cluster with 5 clicks

 

From Raspberry PI 2 Cluster Case pt1, I drew up a rough sketch with certain goals I set out to. They are,

  1. Able to fit in 6 RPI2 in a small, contained volume.
  2. Has to be stackable.
  3. Able to fit in a power supply and a 8 port network switch for the 6 RPI2.
  4. Able to cool off the cluster with no fan.
  5. Has to be cheap.

Prototyping

I then cut out an Acrylic panel at a near laser shop.

Two RPI2 on a cluster panel

The panel have two big round holes for ventilation, 8 holes for RPI2 mounts, and 8 more holes for pillar screws.

Once you put pillars, it looked like this.

Pillar Screws and mounts on a cluster panel

I put a giant square hole in the center to put a USB charger as power supply. You can see the two big round holes for heat ventilation.

At this point, I was terrorized with fact that I could not put a USB-to-MicroUSB cable to the center USB charger. You see the square hole is completely closed? I found that the panel blocked the USB charger’s USB socket, rendering the charger useless. What a bummer…

Gah! No way!

Of course, my happy story did not end there. I then put a RPI to see if it fitted in. To my disappointment, the mount was just too high. You see USB ports sticks to the upper level panel, and there is space underneath the RPI? That’s bad.

Long Mount
High Mountain

In fact, the mount was just too Long. I figured a mount should be around 4~5 mm in length. On top of that, I put one too many pillar screws. I had to use only the minimum number of them to maintain structure strength.

All in all, three problems.

  1. Entrance to USB charger.
  2. Appropriate Mount screw.
  3. Minimum # of pillar screws.

The Final Result

After Fixing three issues above, I now have this.

6 Nodes RPI2 Cluster
6 Nodes RPI2 Cluster
pt-9
The cluster from different angle.

Those USB-to-MicroUSB cables are only 30 centimeters in length. They still stand out and take up quite a bit of space. Does anyone know where I can get a shorter cable?

8 Ports Network Switch at the bottom stack
8 Ports Network Switch at the bottom stack

Of course You can put the entire cluster on your desk.

A cluster on a desk
A cluster on a desk

Assessment

I’ve run the cluster closed to two months so far. I’ve experienced neither heat issue nor performance hit. No single node has gone down while I’m running Apache Spark/Hadoop in cluster mode. It has been amazingly stable and easy to operate. Although there are few more issues I like to fix up later. (Especially the USB charger cable.)

Let’s move on to JAVA on Raspberry PI next time!

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Raspberry PI 2 Cluster Case pt1

This is the first post of a series about Raspberry PI 2 BigData cluster case.

  1. Raspberry PI 2 Cluster Case pt1
  2. Raspberry PI 2 Cluster Case pt2
  3. Raspberry PI 2 Cluster Assembly Tutorial
  4. Build Hadoop Cluster with 5 clicks

Once we have bunch of Raspberry PI 2s (RPI2 from now on) and an Apache Spark/Hadoop image file, there is one subtle issue we need to take care of; the case for cluster.

RPI2 Spark cluster running
RPI2 Spark cluster running

Look at my cluster setup. White & black cables tangled up all around. It takes up a lot of space to lay down. Even if RPI2 cluster runs BigData software very decently, I cannot easily recommend you put this mess to on your desk. Something’s got to be done.

First step I took was to test if my current cases were somehow stackable.

Plastic RPI 2 Case
Plastic RPI 2 Cases

It is doable without much hassle, but, as you can see, it is an effective cage to harness the generated heat. If I am to run a cluster in this case for an extended period, chip soldering joints might go wrong permanently damaging a RPI2, not to mention very unstable operating system.

RPI case #2
RPI case #2

So, I bought a second case. It had a unique capacity to keep the lid open to evaporate the heat. Sadly, I could not pile them up.

No way to pile up
No way to pile up

What a mess. 😦  I have to clarify that it is none of case makers’ fault. Raspberry PI is designed as an educational platform with the ease of replacement. You pick *ONE* for your kids to play with. Something goes wrong? Buy another. That’s what 35 USD price tag and credit-card-sized form factor represent from the first place. It’s no wonder all the cases out there are designed for single Raspberry PI.

Then I found this beauty. It was from modmypi.com and looked great. It is very easy to make RPI2 stack to save space, and opened at all sides to let go of heat.

Stackable RPI case (ModMyPi.com)

Just before purchasing the stacker in mass, however, I imagined stacking up six RPI2s in one direction, and wondered how stable that could be. On top of that, if the stacker was that simple, I thought there should be a way to improve it for my particular situation.

Further, I used a USB hub to power up the cluster, but it created more problems than it solved; most USB hubs are underpowered (as low as total 12.5W) for number of RPI2s, it is hard to arrange cables in clean manner. I needed something compact and powerful.

A couple hours of Amazon search found me these babies.

Photive 6 port USB charger
Anker 6-Port USB Charger

They output 50~60W of 5V power, and all have 6 ports. Price ranges from 25 to 35 USD. They are 4 inches (~10 cm) in height, 2.8 inches (~7cm) in width, and 1 inch (~2.5cm) in thickness. They weight 7 ounces (~200g) in average. I just cannot ask more.

I am going to draw up stackable plates, and mill them in CNC for prototyping. We’ll see how things go next time.

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Apache Spark 1.4.0 on Raspberry PI 2 Cluster

This is the second post of a series about Raspberry PI 2 BigData Cluster for OSX.

  1. Apache Spark on Raspberry Pi 2
  2. Apache Spark 1.4.0 on Raspberry PI 2 Cluster
  3. One Step Spark/Hadoop Installer for OSX v0.1.0
  4. Build Hadoop Cluster with 5 clicks

 

In the previous post, I’ve shown you a RPI2 cluster with Apache Spark 1.1.1 that has run for three months. Since Apache Spark 1.4.0 is out a few days ago, I’ve just upgraded the cluster.

Apache Spark 1.4.0 comes with SparkR finally. R has such a strong position in DataScience field that it is no surprise R and Spark merge into one. Among the many benefits this integration brings, DataFrame, the primary data structure for data processing in R, is ranked on the top.  This is such a great news that one can expect higher level of R algorithms eventually appear in SparkR. You can read more technical detail in AMPlab’s post

There are also other features and improvements coming in together such as early result of project Tungsten, prettier job monitoring, and numerous bug fixes.

Spark Web Console
Spark 1.4.0

Since it takes time to collect all the bits from various places, I’ve compiled an RPI image for you below. Also, this image comes with extra goodies; Numpy and Scikit-Learn. The two giant pillars in Python DataScience land, and they usually take a few hours each to compile into RPI2. Here, all compiled and cleanly installed.

Following is the summary of installed items

  1. Scala 2.11.6
  2. Hadoop 2.6.0
  3. Spark 1.4.0
  4. Numpy 1.9.2
  5. Scipy 0.15.1
  6. Scikit-Learn 0.16

Download RPI2 node image : 2015-06-21-rpi-spark140.img.7z

*  [2015-11-08] A new raspberry image will be uploaded. old image is removed for now.

 

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