I'm not OP but I've done this stuff on and off for two decades and I thought I'd toss out some answers.<p>About 20 years ago I got started using a dozen or so surplus Pentium75 desktops and by combining the working parts and best/largest parts I ended up with eight or so nodes with a reasonable amount of memory and local storage.<p>A write up would have been pointless it was pretty much standard like you'd read in any linux magazine of the era.<p>I used one of the PBS options for batching and some homemade stuff to rip audio CDs to mp3 in a distributed manner and completely unproductively fooled around with PVM and MPI. In the old days PVM was stable and easy to use although MPI was predicted to be the wave of the future. In fact today PVM is pretty much dead and everyone uses MPI or the ever popular NIH homemade stuff. "Back in the old days" we did things like spawn off ray tracing jobs semi-manually with bash scripts and perl scripts. You'd write perl that output animated povray files given a frame number and then queue up like 120 ray tracing jobs and then stack them into video and thats how you got a minute of bad ray traced animated movies. Not being much of an artist my animated ray tracing was limited to bad physics demos like mirrored ball bouncing. As most other cluster ops do I calculated a lot of "X+1" and "Is X a prime" to test. Like most screwing around, honestly I just turned a lot of KWh into heat.<p>The wife acceptance factor was incredibly low. Although admittedly I'm still married, to the same awesome woman even. Eventually I got rid of all the machines. But for a year or two it was a lot of fun. I thought the noise level was bad... then I replaced all the boxes with dell towers a few years later that sounded like jet engines. Then IBM 1U rackmount servers P4 surplus around 2010-ish which did a pretty awesome job of running LXC before containerization became "cool". Portability ha ha ha the size of a closet in the middle of my home office, looks like an organized disaster zone. Really looking forward to building a pi cluster to screw around with that'll fit in a shoebox with room to spare. OMG I could build a toy cluster so small I could drop it into my desk drawer when I'm not playing... Oh if I had more time this summer I'm feeling the urge to build another cluster...<p>Power doesn't matter as long as the circuit breaker doesn't pop. At one point I figured I was burning 1100 watts using the dell towers (and yes the room does get warm) which implies running 24x7 would cost me $1100/yr (which is very cheap compared to a training class or many other hobbies, but I digress) however I suspect I never powered up that cluster more than maybe 300 hours. I spent 10x more money on a then new technology 100 meg ethernet switch than I did on the power the system used. Back in the dinosaur era we mostly used hubs which were unswitched one big broadcast region, probably sounds very weird to modern young kids.<p>I can't even begin to list all the stuff I learned. The jump from admin'ing one unix box to admin'ing a cluster is almost as big as the jump from being an appliance user to being a cluster admin.<p>What I didn't learn was the scalability problems of having 10000 nodes, having less than ten generally, I did a lot of setup by hand. Although I did all the OS level stuff automation like homemade scripts, puppet, etc. A lot of cluster admin is related to the "fun" of physical hardware support for 10000 individual boxes and I miss out on that. Also running 24x7 how do you handle dusty air filters or whatever at that scale for day to day operation? Power failure recovery must be non-trivial.<p>Its hard to say "well I'd never have gotten job X except for..." because I might have anyway. As a hobby its been tangentially tied in with my day job on and off since at least the turn of the century.
<a href="https://pi-hole.net/" rel="nofollow">https://pi-hole.net/</a> is my favorite pi software, it's network wide DNS server for ad blocking which I supplement with a bunch of privacy/security lists from <a href="https://github.com/StevenBlack/hosts" rel="nofollow">https://github.com/StevenBlack/hosts</a>. 5% of my traffic was blocked today which is heaps considering it's counting mountains of requests to eg Dropbox's API.<p>It even ran powered straight off my router's usb port, although I just put in a VM now: <a href="https://github.com/benlowry/pihole-extended-hosts" rel="nofollow">https://github.com/benlowry/pihole-extended-hosts</a>
I'm still hoping for someone to build a SBC like the RPi that takes POE for power. USB is convenient for general use, sure, but for something like this cluster it would be ideal to have a single wire in and out.<p>Unfortunately it's probably a chicken-and-egg thing, where POE is too expensive until a lot of boards support it, and boards won't support it because it's too expensive.
Cheap maybe, but if you really use Raspberry Pi a lot, you will find that Pi isn't that robust after all. I installed 20 of them two years ago, so far at least replaced 4 of them during the time. Can't comment on the recent models though.
I want one of these Pi Zero Motherboards, but there has been no update by the company since January<p><a href="http://hackaday.com/2016/01/25/raspberry-pi-zero-cluster-packs-a-punch/" rel="nofollow">http://hackaday.com/2016/01/25/raspberry-pi-zero-cluster-pac...</a><p>Like others, I have a stack of Pi systems doing file storage, DNS ad blocking, webservers, home control monitoring, XMBC, etc. A clean mount would be cool
Instead of always stacking these, with shelves and/or individual standoffs between the boards, wouldn't it be cheaper and easier to just hang them, using some longer horizontal metal rods going through all the boards' mounting holes?
I have a Pi Zero-based 8 node MPI cluster (4 Zeroes, 1 Pi2) that I set up using 8086 Consulting's Clusterhat. In total it gets about 454 Gigaflops, or roughly the speed of a Pentium 4, or maybe two Raspberry Pi 2s.<p>It's my 3rd beowulf, but the first that fits in my hand and runs over USB. I use it mostly for exploring fractal space and attempting to (but usually failing) to approximate pi.<p>Both problems are well suited to doing something in the slow lane. We know Pi to trillions of places, so there's little benefit in a fast machine to calculate it to billions. It's more a great exercise learning problem solving approaches.<p>So far I've managed to get a working monte-carlo based approximation across the node, but it's a terrible approach to approximating pi to anything more than a few places. I've also had some luck with implementing ramanujan-type formulae, and am still working on implementing chudnovsky in distributed forms within the bounds of the zero's RAM limitations.<p>On the fractal side I've only really had time to look at mandelbrot, but I'm looking forward to using it to render animations for julia and to explore henon attractors.<p>[1] - <a href="http://clusterhat.com/" rel="nofollow">http://clusterhat.com/</a>
>One big thing is to make sure atime is disabled, a massively brain dead feature inherited from 1980s Unix that writes to the disk every time you read from a file.<p>That's not a fair criticism of the atime feature. There are lots of use cases where it is desirable.
As far as computing power it's for sure useless, but tag on some kind of wiring hardness/breakout board for the GPIO pins and a redundant power supply and you might have a nice cheap platform to build a control system around.
SETI@home style / GRID-computing could be used to run jobs on numerous idle Raspberry PIs (the location doesn't matter aka no cluster setup needed).
This kind of stuff is what erlang lives for. Perhaps that might be something to consider ? But then again, running a couple of vm's is way better.
Alternatively titled: "How to build a desk toy that functions better as a conversation piece than a practical replacement for a Hyper-V/Xen lab"