From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: Accelerating Linux software raid Date: Sun, 11 Sep 2005 08:00:54 -0400 Message-ID: <43241C76.4030900@emc.com> References: <4323911D.8010307@emc.com> <20050911023518.GD10501@sam.triumf.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20050911023518.GD10501@sam.triumf.ca> Sender: linux-raid-owner@vger.kernel.org To: Konstantin Olchanski Cc: Mark Hahn , Dan Williams , linux-raid@vger.kernel.org List-Id: linux-raid.ids Konstantin Olchanski wrote: >I am now confused. Is somebody trying to save power by adding an i/o >coprocessor? (with it's own power overhead for memory, i/o, etc) > >To me it is simple: > >1) If you have an infinite power budget (big box), you might as well > let the main cpus do the raid stuff. If you are short on power (embedded), > you cannot afford to power an extra processor (+memory and stuff). > >2) If you have rich customers (big box), let them pay for a bigger > main cpu to do the raid, if you want to be cheap (embedded, appliance), > you cannot afford to plop an extra cpu (+support chips) on your custom pcb. > > The actual facts don't support this view since the gap in power consumption is huge. Most of these system on a chip designs provide the main CPU/northbridge/southbridge and extra execution units for a small fraction of one standard CPU. Say under 20 watts for all of the above versus up to (over sometimes) 100 watts for a standard CPU (without its system chip sets).