Paring Down "Watt's Switched On" on a Client's Network

As part of carbon reduction for a client, Creative Concern, I’ve been working on:

• leased-line router consolidation
• server consolidation
• network switch consolidation (using D-Link’s line of green ethernet switches)
• power management on desktop computers (no screen saver but screen backlight switch-off, sleep when idle, scheduled shutdown at 6pm)
• night-time network scan to determine devices not shut down

The network scan is a particularly fun one: MacOS and modern printers all respond to multicast DNS, and so finding devices which are switched on is quite simple. Every night an email is sent (by one of the servers which stays on 24/7) to the staff naming and shaming the devices which were left powered up:

#!/bin/bash

avahi-browse -at \
  | cut -c 14-59 \
  | sort \
  | uniq \
  | mail -s "Named and Shamed: devices left on overnight" everyone@client

I’ve removed a few grep -v statements which filter out things like the servers which are meant to be left on overnight, but those are the essentials.

Having fitted a smart meter the client has access to power usage graphs and history, and I’m pleased to be able to report that they look to be on course for a 10% saving in 2010! Here is the screenshot from the meter just now:

I am still to explore:

• consolidating the font, finance and project management system servers (currently all require different versions of OS X)
• wireless network access point consolidation (can just two APs cover the entire office area?)
• more network switch consolidation (eliminate all desktop switches?)
• CPU scaling on servers to use power-saving governors outside office hours

I estimate that we might achieve an additional 10% saving if we can do all these things, but could be hampered by what’s feasible in the office with the technologies available.