nanog mailing list archives
RE: Forcasts, why won't anyone believe them?
From: Roeland Meyer <rmeyer () mhsc com>
Date: Tue, 16 Jan 2001 19:49:45 -0800
The assumption is wrong. A server motherboard and CPU draws the same power regardless of what it's doing. Lap-tops and the like are different and you actually pay extra for that design. Most circuts these days are nmos technology. Only in cmos does the power go up with the frequency. Peripheral usage, like disk drives, are also constant since the largest power draw goes to keeping them spinning. The seek mechnics are trivial. Floppy drives and cd-rom drives are different. But, most servers do not keep those spinning constantly. Ergo, for all intents and purposes, servers are a constant power draw. They can be rated. But, isn't this a topic for the DataCenter list?
-----Original Message----- From: Jeff Cours [mailto:jeff () ultradns com] Sent: Tuesday, January 16, 2001 4:18 PM To: nanog () merit edu Subject: Re: Forcasts, why won't anyone believe them? Sean Donelan wrote:One thing that would help. Sun, Dell, Cisco, Compaq, Juniper, etc. Can you pleasestart listingthe true power draw of your equipment, not just the fuse rating. It would make forcasting a lot easier, if we knew ahead oftime how muchthe equipment will really draw.I'm not sure they can. Doesn't the actual power draw of a piece of equipment depend on what it's doing? For example, a rack full of Pentium III's that are acting as routers are mostly doing integer calculations, running bus transceivers, and driving communications links. That same rack full of Pentium III's acting as a render farm for your favorite Hollywood movie will be doing floating point intensive calculations, wide-spread memory access, spinning the disk drives, and, because of the extra heat, working any variable-speed cooling fans harder. I'd expect a measurably higher current draw in the second case. It might be possible to come up with some sort of average power draw, but Electrical Engineers really hate to give out numbers like that because people base their designs on them instead of on the worst case power draw, and then when something fries the EE winds up getting the blame. That's why most engineering disciplines derate components and allow a safety margin, which I suspect is where the fuse rating comes from. - Jeff -- Jeff Cours Senior Engineer UltraDNS, Inc
Current thread:
- Forcasts, why won't anyone believe them? Sean Donelan (Feb 24)
- Re: Forcasts, why won't anyone believe them? Jeff Cours (Feb 24)
- Re: Forcasts, why won't anyone believe them? Brian (Feb 24)
- Re: Forcasts, why won't anyone believe them? Brian Wallingford (Feb 24)
- <Possible follow-ups>
- Re: Forcasts, why won't anyone believe them? Richard A. Steenbergen (Feb 24)
- Re: Forcasts, why won't anyone believe them? John Fraizer (Feb 24)
- RE: Forcasts, why won't anyone believe them? Roeland Meyer (Feb 24)
- Re: Forcasts, why won't anyone believe them? Chris Adams (Feb 24)
- Re: Forcasts, why won't anyone believe them? Alex (Feb 24)
- Re: Forcasts, why won't anyone believe them? Peter Bierman (Feb 24)
- Re: Forcasts, why won't anyone believe them? Valdis . Kletnieks (Feb 24)
- Re: Forcasts, why won't anyone believe them? Marshall Eubanks (Feb 24)
- Re: Forcasts, why won't anyone believe them? Chris Adams (Feb 24)
- Re: Forcasts, why won't anyone believe them? Jeff Cours (Feb 24)
- RE: Forcasts, why won't anyone believe them? Brian Wallingford (Feb 24)