[Beowulf] A Cluster of Motherboard.

[Robert G. Brown]

On Thu, 10 Nov 2005, Josip Loncaric wrote:

> A cheap bare case can cost less than $20 -- and can save you a lot of work, 
> although perhaps not shelf space.  For safety, ease of installation, and FCC 
> EM reasons, cheap metal cases should be considered.

Yeah, I think that Jim's observation that you should think carefully
about the diminishing returns of building a freeform caseless cluster is
very apropos -- you'll save a bit of money on space and cases -- maybe
-- at the expense of more hands on work building the cluster and at the
risk of having to resolve problems with shielding and so on.  For a
>>professional<< grade cluster I'd generally not recommend this approach
unless you are truly working with a shoestring budget and have a metal
shop handy or are building a hobby/learning cluster and want the entire
cluster to be "visible" and supercheap.

In this latter case, you can probably get by by taking sheets of steel
or aluminum, drilling them out using the mounting holes of the
motherboard as a template, and mounting the motherboards on them using
the standard spacers and screws just LIKE a case.  You can then get
creative in several ways as to just how you insert the plates into metal
shelving or even a metal file cabinet drawer with suitably mounted fans
so that each board is cooled, powered, and still reasonably well EM
shielded from the others.  I doubt that you'll save much money (I'm
CERTAIN you won't save money if you bill your own time into the project
even at minimum wage and you'll lose big if you "charge" the
$50-100/hour your time is probably worth:-).

One other thing to watch that I think that Jim brushed up against is
your power supply wiring and ground vs neutral.  If you have three or
four power supplies, each plugged into a different circuit, those
circuits can easily have different phases.  If you are not careful and
do not know what you are doing, there are a variety of ways to create
spectacularly dangerous conditions -- ground loops and worse -- where by
spectacular I mean that "when you plug it in it will explode in a shower
of vaporized and melted metal".  Cases and case power supplies are
designed to be pretty safe -- plug it in and snap on connectors that
really can only work one way.  If you go anywhere beyond this, I'd
REALLY recommend that you only proceed if you completely understand
electricity and electrical wiring and know what a ground loop IS and so
on.

     rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu