Hi !

I have classrooms filled with PXE booted PC's.
As many students always left PC on, i want to try some powersaving.

1-Is it better to get suspend on ram or suspend to disk ?

2-Will the PC resume on mouse click or key push ?

3-When suspended, is there a way to wake up the PC from the network ?

4-Will PXE may introduce some trouble i can't think of now ?

Hi there,

1) Depends what you mean by "better".. Better power savings when machine is not in use for extended period of time comes from suspend to disk, since the machine basically shuts completely off. With suspend to RAM, the RAM is still powered up when machine is "off", so there's a slight larger power draw when suspended to RAM. Another thing is, if suspended to RAM, all can be lost if the power goes out or the battery dies (laptops), but with suspend to disk, you can have a power loss yet still resume from suspend.

2) Depends on the BIOS I believe, and the suspend method. Machine BIOS often will have an option(s) for what actions will cause a resume, i.e. a keystroke, a mouse movement, an RTC event (real time clock).. Now, on my own desktop machine, I have it set to resume from RAM by a keystroke (I hit CTRL to wake it) but not mouse (in case I bump mouse, I don't want machine to awake) but my machine will not awake from suspend to disk or from StandBy mode using the keyboard - I have to press power button to resume it. Again, this probably varies by machine.

3) Yes - It's called WOL, or "Wake on LAN", and requires a "magic packet" be broadcast across the network, targeted at the IP and MAC address of the sleeping machine. I'm not sure exactly how to implement this, but I have seen a few recent threads around here on this very topic, so do some research about WOL, and a check of your machine's user manuals or look in the BIOS to see if your machines have this feature.

4) No idea..

Good luck!

1-Is the HD resuming very fast ? My PXE Slackware 64 boots in 25 seconds.

2-3-Oh i never though suspend/resume were linked to BIOS and WOL ^^. Pretty easy to resume :^).

Thanks for answering.

I don't regularly, and haven't used lately, the suspend to disk, so I can't give you a good idea how relatively fast a resume from disk would be compared to other methods. However, resuming from RAM is really fast -- I never timed it, but the resume itself only takes a few seconds, though the suspend/resume script I use does make the resume take a little longer because it restarts networking and some other crap.

Hopefully someone else who does use s2RAM regularly, can comment on how fast (or not) it is for them.

As for 2-3 above: yes, the BIOS plays a role, because remember, when the machine is suspended whichever way (RAM, disk, etc..) there is no OS actually running, so software cannot play a role in the resume action; it's all BIOS and hardware doing the resume.