From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.gentoo.org ([140.105.134.102] helo=robin.gentoo.org) by nuthatch.gentoo.org with esmtp (Exim 4.62) (envelope-from ) id 1IBCa5-0002ie-PC for garchives@archives.gentoo.org; Wed, 18 Jul 2007 16:40:54 +0000 Received: from robin.gentoo.org (localhost [127.0.0.1]) by robin.gentoo.org (8.14.0/8.14.0) with SMTP id l6IGceOA028492; Wed, 18 Jul 2007 16:38:40 GMT Received: from an-out-0708.google.com (an-out-0708.google.com [209.85.132.245]) by robin.gentoo.org (8.14.0/8.14.0) with ESMTP id l6IGW3DL021540 for ; Wed, 18 Jul 2007 16:32:03 GMT Received: by an-out-0708.google.com with SMTP id c8so54708ana for ; Wed, 18 Jul 2007 09:32:03 -0700 (PDT) DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=NJ7duSImyXyp/Pj8SHv2+dPuvBtY5nVo3Q5MKQqo3LyaSJXmMMd2QfISxYE8n3YDwMZhqP7VbCk/xu/DV2LpZgXmL3dxdrHr5hz67gC0Z1nv5iL7/yCDck6+smw94s8Wf26HaqSlkfqO9YmAoUUIFk5ZwftMXPT3b0Ekvh/c0bw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=H7NtqtL8DQR8ynC9jjZIweEyTh2IxGK1NhdVWDvjyUK4IqIneYnysknpmhHrSCo+pV1XWnxRuejtk+KTwvEfPQcdSeXoGcTth+MpvSixX+od2+XwLKFC9SOwg7blKiLthrqtj9sen0/3gkCtrSJYfXClADW+UKgCwzGWSPn2ZOA= Received: by 10.100.166.14 with SMTP id o14mr1037188ane.1184776323036; Wed, 18 Jul 2007 09:32:03 -0700 (PDT) Received: by 10.100.120.9 with HTTP; Wed, 18 Jul 2007 09:32:02 -0700 (PDT) Message-ID: <6c9e6bf80707180932v6b9c8827jf99f868be36f0076@mail.gmail.com> Date: Wed, 18 Jul 2007 09:32:03 -0700 From: "Julian Simioni" To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Re: Linux becomes expensive ;) In-Reply-To: <64e8d2f20707180844o253d5043j6bc4150d487a7a17@mail.gmail.com> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200706021955.27607.f.philipp@addcom.de> <200706031824.52213.f.philipp@addcom.de> <64e8d2f20706031006w4fcc6053u90163d6153208430@mail.gmail.com> <200706031937.22522.f.philipp@addcom.de> <20070603124921.257cb28a@pascal.spore.ath.cx> <64e8d2f20707180844o253d5043j6bc4150d487a7a17@mail.gmail.com> X-Archives-Salt: d1269051-f8a0-4608-94ac-5baa1149e5d0 X-Archives-Hash: 47904c329b3332f1ea4330f099832817 On 7/18/07, Ryan Sims wrote: > On 7/18/07, Hendrik Boom wrote: > > On Sun, 03 Jun 2007 12:49:21 -0500, Dan Farrell wrote: > > > > > it takes just as much power to > > > spin up the drive as to keep it spinning for a few extra minutes. > > > > So ... spin it down after a few more minutes? > > > > -- hendrik > > No, only spin it down when the savings from the down cycle outweigh > the power cost of spinup+spindown (I don't know whether spindown uses > extra power, to "brake" the drive or anything). > > Say you have a drive that uses 1W/m (huge, but I'm being merciful to > my math skills) while in usage, and requires 5W to spinup. If you're > going to shut it down for 1m, you're looking at saving 1W and using > 5, net use of 4, when leaving it spinning would only use 1. However, > if it's going to be inactive for 30 min, you're using 5 and saving 30, > net savings of 25. > > -- > Ryan W Sims > -- > gentoo-user@gentoo.org mailing list Ryan, You're certainly right that hard drives take more power to start up but I think the arbitrary values you used don't quite represent what really goes on. First though, let me help you with your units. Watts, a unit measuring power, is defined as energy per time period. A device that requires 5 watts and runs for 1 minute will use the same amount of energy as a 10 watt device running for 30 seconds. I think what you really meant to use was Joules, which measures energy. 1 joule per second is one watt. Now, as for the wattage values you supplied. A quick question posed to google lead me to http://www.digit-life.com/articles2/storage/hddpower.html where you can see a listing of power consumption for various hard drives (mostly models that would be used in servers, but they will do) when idle, under use, and most importantly at start up. Looking at the values, it seems that saying a drive uses 12W while active, 8W while idle, and 30W at startup seem reasonable. I don't see anything indicating how long a drive takes to spin up, but I would assume it's something rather short. Let's say 5 seconds (which is probably longer than it actually takes). So here is your hard drive, happily powered up but idle, using 8 watts of power. Since it is idle, you might be wondering if it should be turned off to save power. Since it seems a drive uses 30 watts for 5 seconds when powering up, this is 30x5 or 150 joules. At 8 watts, it will take 150/8 or 18.75 seconds to use 150 joules. Therefore, if this hard drive is going to be idle for more than 18.75 seconds it makes sense to shut it off. Of course real drives will almost certainly be different, but the point is it only would seem to take a few seconds of idle time before powering down makes sense. Also one could argue that this doesn't take into account the effects of wear and tear when stopping/starting drives, but I personally believe those effects are negligible. Finally, an interesting thing about hard drives is that when they are spinning down (at least when power has been unexpectedly cut off), the motor that spins the platters is used as a generator, taking the energy of the spinning drive to move the read/write heads to the parked position, so there is no power cost associated with powering down a drive. Julian -- gentoo-user@gentoo.org mailing list