[Beowulf] Newbie Question: Racks versus boxes and good rack solutions for commodity hardware

Lux, James P james.p.lux at jpl.nasa.gov
Sun Dec 14 08:24:03 PST 2008

On 12/13/08 3:48 AM, "arjuna" <brahmaforces at gmail.com> wrote:

> Hello All,
> Thank you for your detailed responses. Following your line of thought, advice
> and web links, it seems that it is not difficult to build a small cluster to
> get started. I explored the photos of the various clusters that have been
> posted and it seems quite straightforward.
> It seems I have been siezed by a mad inspiration to do this...The line of
> thought is t make a 19 inch rack with aluminum plates on which the mother
> boards are mounted.
> The plan is first to simply create one using the old computers i have...This
> can be an experimental one to get going...Thereafter it would make sense to
> research the right mother boards, cooling and so on..
> It seems that I am going to take the plunge next week and wire these three
> computers on a home grown rack...
> A simple question though...Aluminum plates are used because aluminum is does
> not conduct electricity. Is this correct?

No.. Aluminum is a good conductor.
Aluminum is used because it's cheap and easy to work with and doesn't rust.
Steel is even cheaper, but harder to work with handtools, heavier, and it
needs to be painted.

> Also for future reference, I saw a reference to dc-dc converters for power
> supply. Is it possible to use motherboards that do not guzzle electricity and
> generate a lot of heat and are yet powerful. It seems that not much more is
> needed that motherboards, CPUs, memory, harddrives and an ethernet card. For a
> low energy system, has any one explored ultra low energy consuming and heat
> generating power solutions that maybe use low wattage DC?

In general, the efficiency of line voltage AC to DC power supplies is higher
than DC to DC converters, especially once you factor in the need to get the
DC that the DC/DC converter starts with.  It's a matter of IR losses on the
primary side, mostly.

For beowulfery, especially for novices, you're looking for inexpensive
commodity consumer gear, and that's the standard PC power supplies.

As far as the overall power consumption goes, total up the consumption of
all the pieces, and it adds up fairly fast.  One can use low power devices
(e.g. Like those used in battery powered applications such as notebook
computers), but typically, you also take a performance hit.  Since the vast
majority of clusters are not battery powered, and you're interested in
computational speed, there's no advantage in replacing 5 standard PCs with
10 lowpower, low speed PCs.

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