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| === Turning computers off if nobody is logged in === |
Switching computers into low power states when they are not doing useful work is more problematic than turning off a light bulb or television. People familiar with the way institutional computers are used and managed will recognise at least some of the following practices:
- Users may be asked to leave their computer on for at least one day a week so that a central backup service can make a copy of files overnight
- Computers may need to be left on all the time in case there is the need to install software updates or security patches
- Users leave their computer of all the time so that they can use it remotely to for instance retrieve a file while at a conference
- Computers are left on overnight so that people do not have to wait for it to start up or boot in the morning
- Too many applications are open at the end of the day for a person to find the time to shut them all safely
- Desktop computers are used as a web server or file store
- Desktop computers are used to keep another computer on
- Computers are used to constantly filter emails so that web-based email clients are organised and more easy to use
- Spare computing capacity is 'scavenged' by computer modelling projects e.g. SETI, climateprediction.net and GRID experiments in general
- Standby (S3) and hibernate (S4) power saving modes cause issues serious enough that ICT managers are forced to disable automatic power management entirely.
This section of the Low Carbon ICT wiki describe tools and practices for reducing the energy that is wasted by leaving computers on when they are not doing useful work.
Tools and practices
Waking computers remotely
A wake-on-LAN (WoL) service allows people to switch a computer on without having to be physically in the same location. By providing a facility that can be used to switch computers on 'remotely' it becomes possible to safely switch computers into low power states more often. For instance, many organisations will ask staff to leave computers on to allow backup and software patching services to access their computers. If computers can be switched on by these backup and patching services, users can switch their machines off without disrupting this essential activity.
Case study: University of Oxford's WoL infrastructure
[http://wiki.oucs.ox.ac.uk/ltg-public/lcict:wol_oxford_university The University of Oxford wake-on-LAN infrastructure] enables ICT managers, end-users and managers of third-party services to wake computers remotely. The WoL service is being used so that members of the University can be asked to switch their computers to low power states (off, standby or hibernate) when they are not in use.
Configuring computers to move into low power states automatically
Desktop computers have four main power states: On (S0) Sleep or standby (S3) Hibernate (S4) Off (S5). Most computing devices are built to be able to detect when they are not being used. There are however a number of issues associated with the way that power saving capabilities have been implemented:
Test cases: The purpose of this document is to describe a way to gather structured test-case data about implementing power management on desktop computers
- Can you configure computer to automatically go into S3 or S4 mode automatically?
- Does computer drop to S3 and S4 after pre-configured time unit?
- Does computer stay in S3 and S4 if you do not switch it back on e.g. using WoL, pressing power button, moving mouse/ pressing a key?
Switching computers off automatically
Case study: Switching computers off automatically at Liverpool University
Configuring standby (S3) and/ or hibernate (S4)
Case study: Configuring computers to move into standby automatically at Liverpool University
Asking users to switch their computers off
Case study: Asking users to switch their computers off at the University of Oxford Case study: Asking users to switch their computers off at the University of Leeds
Disable screen savers
Turning computers off if nobody is logged in
Only switch computers in clusters on as needed
Switching computers on automatically at pre-configured time
Computers can be woken remotely at a pre-configured time, for instance by a WoL service. This can help where computers are particularly slow to boot from off. Doing this presents the problem that computers may be switched on when they are not needed. This is less of a problem if this policy is coupled with automatically putting computers into S3 mode, or turning them off. People wishing to put computers to sleep (S3) after they have been woken should test to make sure this approach is reliable (some computers may not enter or stay in S3 mode, and consume the same number of Watts as they do when on).
Commercial solutions
Life-cycle considerations
The manufacture and transport of computing equipment results in a considerable amount of CO2 to be released into the atmosphere, many of the components are considered toxic waste and have to be carefully recycled, and the manufacture of circuit components requires large volumes of clean water. With this in mind it becomes obvious that for any organisation to truly improve its environmental performance it will have to carefully control its procurement processes.
Extend the life-cycle
Buy equipment that will perform useful work for the longest period of time. Notes: warranty, system maintenance to improve performance.
Promote greater sharing of resources
Organisations can reduce their carbon footprint by buying fewer devices and asking people to share equipment more often.