
Raspberry Pi 2 Cluster Case, Part 2 - stkim1
https://pocketcluster.wordpress.com/2015/07/23/raspberry-pi-2-cluster-case-pt2/
======
Quequau
Sometimes I get the feeling that I'm the only person who feels like these
single board computers that use ARM SoCs designed for mobile devices have
insufficient interconnect capability. The networking that these devices have
always seems like an afterthought. For example a lot of these SoCs have the
nic hanging off an internal USB port, which is a fairly convoluted way to go
about things.

I really wish there were single board RPi / ODROID like devices available that
sported support for a really performant and efficient interconnect fabric...
like RapidI/O or something similar.

~~~
legulere
Storage also is also such an issue. You also usually only get sata via USB.
SATA and/or PCIe would be really nice to have

~~~
stkim1
In fact, storage is a big issue. RPI tends to destroy SD card in a way that a
cluster like mine isn't exactly safe unless you put high-grade SD card and
very reliable power source. Those contribute somewhat higher operation cost
which violate the purpose of these single board computer.

~~~
paulmd
I've been really unsuccessful at getting a Pi to not destroy SD cards. Good
quality cards, good quality power supplies, no swapping - it still eats them
up.

The best way to fix this is to put the actual OS on an external disk. You
absolutely must bootstrap from an SD card, there's no way around that. But
that can be entirely read-only and then you bounce to the external drive. Or
maybe you could do something like a PXE boot instead - copy a system image
down from a server and boot that. Personal opinion, this is the only way I
would try using Pis on a long-term basis.

The Jetson TK-1 board from NVIDIA includes a real SATA connector. Because it's
GPGPU-capable it's also vastly more powerful than even a Pi2. It also has USB
3.0 so running swap on a memory stick would be much more performant.

~~~
stkim1
PXE boot is something I thought about, but I don't know if it is possible on
RPI. Do you have any link where I can just go read up about that?

~~~
paulmd
[http://blogs.wcode.org/2013/09/howto-netboot-a-raspberry-
pi/](http://blogs.wcode.org/2013/09/howto-netboot-a-raspberry-pi/)

[http://www.whaleblubber.ca/boot-raspberry-pi-
nfs/](http://www.whaleblubber.ca/boot-raspberry-pi-nfs/)

~~~
stkim1
Thank you!

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ericmo
I see @stkim1 is also the author of the blog. Performance-wise, how does this
RPi cluster compare to a more standard platform? Did you make it only as a
development platform or do you intend to have production code running in it?

~~~
stkim1
I've never imagined the RPI cluster to be taken seriously for production
purpose. It only serves two purposes; education and developmental staging. For
those two, you have a real hardware cluster that serves you superbly showing
every nature you can experience with big-ass datacenter cluster.

~~~
detaro
What do you think about using a cluster of VMs on a normal PC as an
alternative? Did you look into that?

~~~
stkim1
I'm looking into that. When you have a lot of memory, it's in fact more
convenient in a way that you can carry the entire cluster in your laptop. lol

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rwmj
Those little aluminium pillars are brilliant. You can see my (real PC) cluster
here that I built using bare motherboards and pillars:

[https://rwmj.wordpress.com/2014/04/28/caseless-
virtualizatio...](https://rwmj.wordpress.com/2014/04/28/caseless-
virtualization-cluster-part-5/#content)

~~~
stkim1
You are da man. This is really cool! I can only imagine how much you've been
through!

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pedjak
More Raspberry clusters [http://www.datastax.com/dev/blog/32-node-raspberry-
pi-cassan...](http://www.datastax.com/dev/blog/32-node-raspberry-pi-cassandra-
cluster)

~~~
stkim1
David Guill is another deadly serious RPI cluster builder. I don't know what
he's running, but I can only admire what he had done.

[http://likemagicappears.com/projects/raspberry-pi-
cluster/](http://likemagicappears.com/projects/raspberry-pi-cluster/)

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ansible
I've been tempted several times to build a small cluster of low-power boards
for a compute cluster. Not that I have much direct use for that at the moment.
I recently got a new laptop with 16GB of RAM, so just running 8 VMs with 1GB
of RAM each still leaves plenty left for development. With the VMs, I can just
run regular 64-bit Linux, so that makes software and setup a non-issue.

I've got so many other projects on the back-burner I shouldn't even be reading
about this sort of thing. But it does look fun!

~~~
icpmacdo
With 1GB of ram there are no problems running 64bit linux? I thought you
needed 4+.

~~~
ansible
Yes, you can run 64-bit Linux with even less if you like, and that is quite
common. [0]

More RAM is always nice, of course.

[0]
[https://www.digitalocean.com/pricing/](https://www.digitalocean.com/pricing/)

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kcbanner
What is the use case for clustering Raspberry PIs? Why not build a more
powerful computer within that same footprint?

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bodyfour
As a productive tool, I can't think of a use at all.

For learning distributed computing, I think has some advantages over just
running all of the nodes on a single powerful computer. It means you can't
hide from doing things scalably -- i.e. network costs between your processes
are real; if your load isn't well-distributed across your nodes the OS
scheduler can't save you; etc.

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systemz
Raspberry Pi cluster? Average PC with virtualization would be better and
probably cheaper choice.

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rco8786
Startech.com sells 15cm micro USB cables, they work great with my Pis.

~~~
stkim1
Thank you very much! I'll look into that!

