From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Freemyer Subject: Re: Adding more drives/saturating the bandwidth Date: Tue, 31 Mar 2009 09:05:46 -0400 Message-ID: <87f94c370903310605p893c6ces5ae3ee4e274c3b22@mail.gmail.com> References: <87eiwf81e8.fsf@frosties.localdomain> <439371.59188.qm@web51306.mail.re2.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <439371.59188.qm@web51306.mail.re2.yahoo.com> Sender: linux-raid-owner@vger.kernel.org To: Jon@ehardcastle.com Cc: Goswin von Brederlow , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, Mar 31, 2009 at 4:23 AM, Jon Hardcastle wrote: > > --- On Mon, 30/3/09, Goswin von Brederlow wrote: > >> From: Goswin von Brederlow >> Subject: Re: Adding more drives/saturating the bandwidth >> To: Jon@eHardcastle.com >> Cc: linux-raid@vger.kernel.org >> Date: Monday, 30 March, 2009, 4:40 PM >> Jon Hardcastle writes: >> >> > Hey guys, How do you know if your machine can handle >> adding some more drives to it? How can you check that there >> is enough BUS IO to handle extra sata cards and also that >> the machine is powerful enough to support say an 8 drive >> raid 5... >> >> A) Try & error. >> B) look up the speed of the bus and half it. Any bandwidth >> left? >> =A0 =A0make sure the cpu isn't at 100% already as well >> >> MfG >> =A0 =A0 =A0 =A0 Goswin > > Cheers guys, I dont think CPU will be an issue as when i looked yeste= rday whilst copying to my 6 drive raid 5 array it was at ~10% (the only= time i get access issues is when i am smart checking all 6 discs and t= rying to stream a movie of it at the same time!) > > As for try and error... sounds scary as once I have added a drive to = the array I can undo the process! What do you think the "ran out of bandwidth" error is. You make it sound fatal. Not true, it is just a bottleneck. So if you design your system to max out the bus structure with a a random i/o load, but then you perform a large sequential load, the sequential workload will just under perform what you would expect based on the disk drives themselves. No big deal as long as you design and test based on your real world wor= kload. Greg --=20 Greg Freemyer Head of EDD Tape Extraction and Processing team Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer =46irst 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.p= df The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html