[wellylug] diskless headless

[Bruce Hoult]

On Thu, Nov 4, 2010 at 2:07 PM, E Chalaron <e.chalaron at xtra.co.nz> wrote:
> Hi Tim
>
> Well I don't even know where to start ...
> Let's say ideally 1 would have a disk with a complete system and the
> soft I am using the other 4 just CPU power.
> I still have a question before getting any further : how efficient is
> clustering for this type of jobs, e.g. munching numbers non stop.
> Is there a relation between the amount of boxes working together versus
> 1 big CPU like a i7?

In general it depends on how much communication is needed vs how much CPU.

You're doing something to a lot of individual images? That's what's
known as "embarrassingly parallel". Ethernet is fine for
communication. Just find the cheapest and/or lowest power way to buy
lots of MIPS. The power may be the driver, both for the running cost
itself, but also for cooling.

I love my homebuilt i7 860 machine. Running at 3.84 GHz (on the stock
cooler) it's using 80W at idle with the cores at 51 C. That's the
normal state. Under full load (e.g. highly parallel compile with -j 8,
or processing video with HandBrake) it gets up to 145W and the cores
get up into the 90's and hit 100 C with a tiny bit of inserted wait
states occasionally. I've run it like that for 24 hours or so, batch
processing all my ripped DVD images to H.264 and it was perfectly
stable.

If I was going to run it flat out all the time I'd probably back it
off to 3.33 GHz where the core temps only get into the 80's.

At the other extreme, Mac Mini's have a 2.4 GHz Core 2 Duo and use 8 W
at idle and about 20 W when working hard. Four of them would probably
match or beat the i7 for speed on your task while using a lot less
space and power than a tower. But the capital cost would be high.

For reference, my Core i7, if run flat out 24/7, would use $250 of
electricity in a year.  I don't know how much aircon would cost to run
if you had enough of them to need it.