Rasberry pi - high density
Rafael Possamai
rafael at gav.ufsc.br
Tue May 12 15:05:24 UTC 2015
Here's someone's comparison between the B and B+ in terms of power:
http://raspi.tv/2014/how-much-less-power-does-the-raspberry-pi-b-use-than-the-old-model-b
On Mon, May 11, 2015 at 10:25 PM, Joel Maslak <jmaslak at antelope.net> wrote:
> Rather then guessing on power consumption, I measured it.
>
> I took a Pi (Model B - but I suspect B+ and the new version is relatively
> similar in power draw with the same peripherials), hooked it up to a lab
> power supply, and took a current measurement. My pi has a Sandisk SD card
> and a Sandisk USB stick plugged into it, so, if anything, it will be a bit
> high in power draw. I then fired off a tight code loop and a ping -f from
> another host towards it, to busy up the processor and the network/USB on
> the Pi. I don't have a way of making the video do anything, so if you were
> using that, your draw would be up. I also measured idle usage (sitting at
> a command prompt).
>
> Power draw was 2.3W under load, 2.0W at idle.
>
> If it was my project, I'd build a backplane board with USB-to-ethernet and
> ethernet switch chips, along with sockets for Pi compute modules (or
> something similar). I'd want one power cable and one network cable per
> backplane board if my requirements allowed it. Stick it all in a nice card
> cage and you're done.
>
> As for performance per watt, I'd be surprised if this beat a modern video
> processor for the right workload.
>
>
> On Mon, May 11, 2015 at 5:16 PM, Rafael Possamai <rafael at gav.ufsc.br>
> wrote:
>
> > Maybe I messed up the math in my head, my line of thought was one pi is
> > estimated to use 1.2 watts, whereas the nuc is at around 65 watts. 10
> pi's
> > = 12 watts. My comparison was 65watts/12watts = 5.4 times more power than
> > 10 pi's put together. This is really a rough estimate because I got the
> > NUC's power consumption from the AC/DC converter that comes with it,
> which
> > has a maximum output of 65 watts. I could be wrong (up to 5 times) and
> > still the pi would use less power.
> >
> > Now that I think about it, the best way to simplify this is to calculate
> > benchmark points per watt, so rasp pi is at around 406/1.2 which equals
> > 338. The NUC, roughly estimated to be at 3857/65 which equals 60. Let's
> be
> > very skeptical and say that at maximum consumption the pi is using 5
> watts,
> > then 406/5 is around 81. At this point the rasp pi still scores better.
> >
> > Only problem we are comparing ARM to x86 which isn't necessarily fair (i
> am
> > not an expert in computer architectures)
> >
> >
> >
> >
> >
> > On Mon, May 11, 2015 at 5:24 PM, Hugo Slabbert <hugo at slabnet.com> wrote:
> >
> > > Did I miss anything? Just a quick comparison.
> > >>
> > >
> > > If those numbers are accurate, then it leans towards the NUC rather
> than
> > > the Pi, no?
> > >
> > > Perf: 1x i5 NUC = 10x Pi
> > > $$: 1x i5 NUC = 10x Pi
> > > Power: 1x i5 NUC = 5x Pi
> > >
> > > So...if a single NUC gives you the performance of 10x Pis at the
> capital
> > > cost of 10x Pis but uses half the power of 10x Pis and only a single
> > > Ethernet port, how does the Pi win?
> > >
> > > --
> > > Hugo
> > >
> > >
> > > On Mon 2015-May-11 17:08:43 -0500, Rafael Possamai <rafael at gav.ufsc.br
> >
> > > wrote:
> > >
> > > Interesting! Knowing a pi costs approximately $35, then you need
> > >> approximately $350 to get near an i5.. The smallest and cheapest
> desktop
> > >> you can get that would have similar power is the Intel NUC with an i5
> > that
> > >> goes for approximately $350. Power consumption of a NUC is about 5x
> that
> > >> of
> > >> the raspberry pi, but the number of ethernet ports required is 10x
> less.
> > >> Usually in a datacenter you care much more about power than switch
> > ports,
> > >> so in this case if the overhead of controlling 10x the number of nodes
> > is
> > >> worth it, I'd still consider the raspberry pi. Did I miss anything?
> > Just a
> > >> quick comparison.
> > >>
> > >>
> > >>
> > >> On Mon, May 11, 2015 at 4:40 PM, Michael Thomas <mike at mtcc.com>
> wrote:
> > >>
> > >> As it turns out, I've been playing around benchmarking things lately
> > >>> using
> > >>> the tried and true
> > >>> UnixBench suite and here are a few numbers that might put this in
> some
> > >>> perspective:
> > >>>
> > >>> 1) My new Rapsberry pi (4 cores, arm): 406
> > >>> 2) My home i5-like thing (asus 4 cores, 16gb's from last year): 3857
> > >>> 3) AWS c4.xlarge (4 cores, ~8gb's): 3666
> > >>>
> > >>> So you'd need to, uh, wedge about 10 pi's to get one half way modern
> > x86.
> > >>>
> > >>> Mike
> > >>>
> > >>>
> > >>> On 5/11/15 1:37 PM, Clay Fiske wrote:
> > >>>
> > >>> On May 8, 2015, at 10:24 PM, charles at thefnf.org wrote:
> > >>>>
> > >>>>>
> > >>>>> Pi dimensions:
> > >>>>>
> > >>>>> 3.37 l (5 front to back)
> > >>>>> 2.21 w (6 wide)
> > >>>>> 0.83 h
> > >>>>> 25 per U (rounding down for Ethernet cable space etc) = 825 pi
> > >>>>>
> > >>>>> Cable management and heat would probably kill this before it ever
> > >>>>> reached completion, but lol…
> > >>>>>
> > >>>>>
> > >>>> This feels like it should be a Friday thread. :)
> > >>>>
> > >>>> If you’re really going for density:
> > >>>>
> > >>>> - At 0.83 inches high you could go 2x per U (depends on your
> mounting
> > >>>> system and how much space it burns)
> > >>>> - I’d expect you could get at least 7 wide if not 8 with the right
> > >>>> micro-USB power connector
> > >>>> - In most datacenter racks I’ve seen you could get at least 8 deep
> > even
> > >>>> with cable breathing room
> > >>>>
> > >>>> So somewhere between 7x8x2 = 112 and 8x8x2 = 128 per U. And if you
> get
> > >>>> truly creative about how you stack them you could probably beat that
> > >>>> without too much effort.
> > >>>>
> > >>>> This doesn’t solve for cooling, but I think even at these numbers
> you
> > >>>> could probably make it work with nice, tight cabling.
> > >>>>
> > >>>>
> > >>>> -c
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>
> >
>
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