"Robert G. Brown" <[EMAIL PROTECTED]> wrote > Google for a "kill-a-watt". Brand new, shipped, it's about $25 (from > e.g. Amazon). A must have for any serious cluster enthusiast or > manager -- use it to plug the systems in and then look. It's one of the > only ways to be sure.
I'll second that recommendation. I used one to make a lot of power measurements on various systems: http://saf.bio.caltech.edu/saving_power.html One thing it taught me is that screensavers WASTE energy, even ones that blank the display. While that worked ok for CRTs (where power usage is proportional to screen brightness) it just sets the pixels to black on an LCD, which saves no energy at all. Far better to let the OS put the monitor into standby, where energy usage is roughly zero. Larry Stewart <[EMAIL PROTECTED]> wrote: > I do agree though, that if you aren't computing anything, then you > may as well unplug the machine. Well, the problem with going from full off to full on is that it's quite slow. Plus they won't always come back up reliable (Cough, Tyan, cough). It would be nice if somebody made a server class CPU with an ultra low power setting - the system would still be running, just very, very slowly. Much faster kicking up the CPU from 100Mhz to 3Ghz than rebooting the system. The normal CPU frequency shifting software could keep an eye on the load and run as slowly, or as quickly, as is possible/required. Also, it's definitely bad to spin disks down and up frequently, but I think mostly the problem is that the disk goes all the way to, stopped and bad things tend to happen there. I wonder if a disk couldn't be built that could slow down from 10K RPM to 5K RPM (or less), and save energy that way. Just keep the platters moving fast enough to float the heads. The time to reposition the heads wouldn't change, although the seek time would be a bit longer waiting for the right piece of data to rotate around. Such a disk could conceivably also monitor its own activity and spin up to full speed when that is warranted. With 8Mb buffers being common I suspect that under a lot of circumstances there would be virtually no difference between the 5K and 10K modes. The flip side of all of this is that if the power usage is going up and down dramatically on the cluster it might cause problems with, for instance, the room's UPS or A/C. Regards, David Mathog [EMAIL PROTECTED] Manager, Sequence Analysis Facility, Biology Division, Caltech _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
