A beowulf cluster is a cluster of computers connected over a network, running linux, and dedicated to computation. This article is the first part of a series on how to build a beowulf. It describes the hardware assembly and costs.
At the university we need big computational power to do simulations, but we don't want to spend huge money on one big and expensive computer. We rather want many cheap computers and have them compute in parallel. The computers are connected in a network and run Linux. This architecture is called a beowulf.
In this post I will describe how we built our beowulf cluster. I'll explain which hardware we chose and some experiences assembling it. In later posts I will describe cluster installation, cloning of configurations, and running parallel processes in matlab and GNU R using MPI and PVM.
I spend a lot of time comparing different hardware. I was fortunate to find a store, specialized in servers, where they helped me with good advice. We bought 8 computers with these parameters:
They cost 923 euros each.
To operate 8 computers efficiently we need a monitor... or better a KVM (keyboard video mouse) with 8 ports, which cost 850 euros.
We also need to connect all the computers among themselves: A switch, 16 ports, 10/100/1000, 162 euros.
We want to put all the hardware somewhere, where it is save and where it has good conditions: a rack. This is our rack. It came like Ikea from the shop, even including easter egg screws that you have to search ;). It can take up 42 units of 19'' and cost us 500 euros.
There came a surprise for us: we need cables, screws(!), and multi-outlet power strips. Rails allow you to stack in and take out your computers like drawers. Additional cost: about 700 euros!
In Spain, they mostly don't give you the real costs. There is IVA (impuesto al valor agregado=value added tax), 18%. About 1500 euros.
Total cost of the beowulf: about 11,090 euros.
We bought computers, we bought a rack, we bought everything we need, but we are in Spain and we are temporarily in an old building. What had to happen? The electricity lines didn't have the capacity to power the computers! While a pile of cardboard boxes started putting on dust, we waited impatiently (especially me) for more than a month. Finally, the technicians fixed the power lines so we have the capacity we need.
So, we mounted everything and the magical moment was starting up all computers and seeing they were running without power failures or explosions.
You see on the photo, there is a lot of light in the room. On top, air conditioning in the room doesn't work and they have to fix it. Fortunately (unfortunately), August with Barcelona's heat is about to end and it becomes already less hot. Maybe in January we will move to another building and hopefully get a better room, where we can run the computers during next summer.
In other posts, I'll explain basics of cluster configuration and parallelization. Until then please enjoy with me a photo of the computer hardware mounted into the rack. You can see the 8 computers flanking from two sides the KVM which is in the middle, behind it the switch. The cluster stands now next to my desk, because in our office both air conditioning and ethernet work.
Book recommendations:
Robert G. Brown's "Engineering a Beowulf-style compute cluster" [online at duke university] (2004) gives you the essentials of the hardware side.
High Performance Linux Clusters with OSCAR, Rocks, OpenMosix, and MPI (Nutshell Handbooks) by Joseph Sloan
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