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Some of the newer DICE computers in the student labs automatically "sleep" when idle and unused, to save electricity.
The University's current strategic plan commits it to "achieving continued reduction of [its] environmental impact". We also hope to lower our electricity bills.
A sleeping machine won't respond to key presses or mouse clicks and its screen will be in a power-saving state. It'll look a bit as if it's simply switched off. However you can tell a sleeping machine by its flashing power button or light: the computer's power button (or a light just beside it) will steadily flash green during sleep.
To wake up a sleeping machine, press the flashing green power button once only, then wait a few seconds. The normal DICE login screen will appear. The machines also wake up automatically from time to time.
You can't currently wake a sleeping DICE machine by pressing a key or clicking a mouse button. This is because these devices are powered off during the DICE machines' sleep state so aren't being listened to. Instead, press the computer's power button once, then wait a few seconds.
Once the power button has been pressed it can take anything between a few seconds and (in extremis) 30 seconds for the machine to wake up fully and display the normal DICE login screen. The time taken varies from one model to another.
Our sleep software uses several criteria when deciding whether or not to send a DICE machine to sleep. In summary, if you're logged in or if the machine is busy doing anything then it won't go to sleep.
The machines wake up automatically every few hours in order to perform automatic system maintenance tasks such as installing new software. A machine will also wake up if you press the power button.
Just logout. If the machine has our sleep software on it, it'll then fall asleep when it's safe to do so. DICE machines have to be awake from time to time to do administrative work such as running cron jobs and installing new software, and our sleep software ensures that nothing important is happening or due to happen before sending the machine to sleep.
Condor uses spare computing cycles on idle machines to run computing jobs submitted by users. While a machine is running a Condor job it won't go to sleep. Only when a machine has been idle for a while will it sleep, and at that point it will leave the Condor pool. However each machine will automatically wake up after a few hours of sleep, and when it wakes it will rejoin the Condor pool and become available for running Condor jobs once again. In this way we think we've made Condor and automatic sleep compatible.
If you spot something wrong please tell Support so we can put it right. Thanks a lot!
At the moment we're being cautious with the Sleep project. We have now deployed it on HP dc7900s in the Student labs. In time we may extend it to other DICE desktop machines - for example those used by staff and postgrad students. In the meantime if you have your own HP dc7900 DICE desktop machine and you're keen to have automatic sleep, please get in touch via Support - thanks!
The sleep state we use is ACPI mode S3. S4 would save even more power but would take a lot longer to wake up from.
We've written an LCFG component which manages sleep automatically. Find out more about it on the LCFG Sleep page on the LCFG wiki.
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