Sunday, 14 October 2012

Raspberry Pi - The Organic Way to a Green Network?

Epilogue to the Previous Post

There was life in my RPi, but not as I planned it Jim!

As a headless box, remotely operated through an SSH session, the Pi worked well - including its raspi-config tool.

But the wireless USB keyboard and mouse not working was my fault.  I didn't check the specs of the peripherals first.  If I had, I would have realised that they were not compatible with Linux.  Have since ordered a new set from Element14.

Going Green

Whilst waiting to get these goodies, I've been doing some thinking and planning.  My testing of the RPi and its abilities against other platforms is still in the planning process..  But in parallel I've had some other thoughts.


Looking at the power bills that we are getting out in a rural region - horrendous.  I'm certain that part of that excessive power usage is my small network of machines at home.  Yet I want to do more from home, with more machines.  That can only mean one thing - a bigger power bill.  Or does it?

Perhaps the RPi can come to the fore here.  Part of the problem is the machinery that I leave running most of the time.  My desktops and laptop are not so much of an issue if I shut them down overnight when not in use.  But looking at my network as it is now, and how I would like it to be, there are several spots in which I might wish to substitute in a RPi.  The list of appliances that I would like to have running 24/7 includes:
  • Firewall/Proxy Server
  • Dedicated Web Server
  • Dedicated Web App Server
  • Dedicated DB Server
  • Dedicated IDS/Honeypot
  • Dedicated Print Server

In considering the suitability of the RPi for any of these roles, I need to be able to compare apples to apples.  To do this from the power supply perspective, we need a way of comparing our traditional desktop power supply of 300 to 400 Watts, to the 1 Amp supply running the RPi.  To do this, we are going to make use of the equation;
          Watts = Amps x Volts
So, how many Watts does the RPi draw?  This is always going to be dependent upon the power pack used.  The power pack that I'm using currently has an output of 1 Amp at 5 VA.  But that is what it outputs to the RPi, not what it draws from the power socket.  What it draws from our power socket is 240 Volts at 150 milli-Amps.  Throwing these values into our equation;
          Watts = 0.15 x 240
          Watts = 36
But of course, I could compare this to a desktop or server with a 1KW PSU, and rave on about how much of a saving it should make, but it is not the size of the PSU that is important, but the amount of hardware that it supports.  From various sites you can utilise an online power calculator.  I went to eXtreme Outer Vision's calculator page.  Here I plugged in the values that were as close as possible to what my existing firewall machine has.  It is running a 300Watt PSU.  I calculated the power draw for it based upon a 90% CPU utilisation and it calculated that it would require a minimum of 198 Watts, but recommended 248 Watts to be sure.  For my comparison, I am going to take the conservative value of 198 Watts.  This is nearly 6 times more than the power draw of the RPi.  I think that there could be some real savings achieved.

To see how these potential solutions turn out, I have started a new page at: Raspberry Pi and Green Home Network