--- On Tue, 31/3/09, Goswin von Brederlow <goswin-v-b@xxxxxx> wrote: > From: Goswin von Brederlow <goswin-v-b@xxxxxx> > Subject: Re: Adding more drives/saturating the bandwidth > To: Jon@xxxxxxxxxxxxxxx > Cc: "Goswin von Brederlow" <goswin-v-b@xxxxxx>, linux-raid@xxxxxxxxxxxxxxx > Date: Tuesday, 31 March, 2009, 10:07 PM > Jon Hardcastle <jd_hardcastle@xxxxxxxxx> writes: > > > --- On Mon, 30/3/09, Goswin von Brederlow > <goswin-v-b@xxxxxx> wrote: > > > >> From: Goswin von Brederlow > <goswin-v-b@xxxxxx> > >> Subject: Re: Adding more drives/saturating the > bandwidth > >> To: Jon@xxxxxxxxxxxxxxx > >> Cc: linux-raid@xxxxxxxxxxxxxxx > >> Date: Monday, 30 March, 2009, 4:40 PM > >> Jon Hardcastle <jd_hardcastle@xxxxxxxxx> > 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? > >> make sure the cpu isn't at 100% already as > well > >> > >> MfG > >> Goswin > > > > Cheers guys, I dont think CPU will be an issue as when > i looked yesterday 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 trying 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! I suppose > I could add them as JBOD's and then thrash the hell out > of them.. whilst accessing the rest of the array... What > does halving the bus speed tell me in anycase? > > Just see if you can get a decent bandwidth from each disk: > > for i in /dev/sd?; do dd if=$i of=/dev/null bs=1M > count=10240 & done > iostat -k 10 > > > Halving the bus speed gives you a reasonable low > expectation of how > much data you should be able to pull of the disks. If your > disks can't > even fill half the bus bandwidth you certainly can cope > with more > disks or something is seriously wrong. > > MfG > Goswin > -- Thank you, can i assume that is a destructive test? :-D ----------------------- N: Jon Hardcastle E: Jon@xxxxxxxxxxxxxxx '..Be fearful when others are greedy, and be greedy when others are fearful.' ----------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
