[MacTUG] Energy saving and maintenance scripts

[Donald Duff-McCracken]

Hi gang

I was having a discussion with Marlon recently and we were talking about my desire to have us all save energy, and his desire to ensure that his maintenance scripts are running in the middle of the night -- I think around 3:15 or so ;-)

I have been have my machine (and our lab machines) set to save a lot of energy, but I need to tweak the settings a bit to ensure that the scripts are running.

I have my macs set to go into sleep mode after about 30 minutes so or. Note that his is actually less efficient than the default, which is 10 minutes. I have them put hard disks to sleep whenever possible and to wake for network access (these two settings are factory defaults). If the computer is kept at the factory defaults (as a bare minimum) the maintenance scripts will run, as the mac is smart enough to wake up to perform the scripts and go back to beddy bye again. So my settings of sleeping after 30 minutes was not the issue.

What was the issue is that I also had the mac scheduled to shut down at 11pm, to save the tiny bit of energy that the mac uses in sleep mode. I have now disabled this function. The energy saving in shutting down versus sleeping is pretty trivial — about 1 watt (1.25 watts vs .25 watts) so it is not really worth it. In fact I did some cocktail napkin sketches, and prematurely starting the mac up (I had them start at 7am so students would not have to wait for them) probably ate any energy savings I was making!!

But it is really important to let your mac go into sleep mode. If you are being old school and not letting your computer sleep, you are wasting a ton of energy (quite literally!) as a mac (e.g. 21" iMac) running in normal mode is using about 40 watts than if it is sleeping. This is one of those instances where being green (and saving energy) also saves us green (as in cash). There are other reasons to do this as well.

  *   We have brownouts and reducing demand on the system is a help for this.
  *   Modern computers last longer if they are not running when in use — knock on wood, I have had only one or two failures  a lab machine or MAD staff desktop computer in the 15 years I have been here (likely representing ~1000 computer-years) and we keep our macs till they are ancient (e.g. I have 7 year old iMacs in the general purpose lab).  I think having them take it easy when they are not being used helps in their longevity.
  *   Lastly, us Mac nerds are always looking for something to be smug about, and the Macs are generally one of the more energy efficient devices out there. I know of users who bought macs because of their vaunted energy efficiency, so we should play this up!

The only downside to having them sleep is if you want to have them perform certain actions in the evening. If that is the case you can set the schedule to have them wake at a certain time, or use ARD to tell them to wake or all sorts of other tasks. I use ARD to perform tasks on my sleeping macs and it is no probs. And to repeat, the maintenance scripts run fine when the mac is sleeping — which totally makes sense as this is the default setting for them.

http://www.apple.com/ca/environment/reports/

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Donald Duff-McCracken
Technical Services Manager
Mapping, Analysis & Design
Faculty of Environment
University of Waterloo
(519) 888-4567 x32151
https://uwaterloo.ca/environment-computing/about/people/donald-duff-mccracken

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