On Wed, Apr 1, 2009 at 11:59 AM, Goswin von Brederlow <goswin-v-b@xxxxxx> wrote: > Jon Hardcastle <jd_hardcastle@xxxxxxxxx> writes: > >> --- On Tue, 31/3/09, Goswin von Brederlow <goswin-v-b@xxxxxx> wrote: >>> Just see if you can get a decent bandwidth from each disk: >>> >>> for i in /dev/sd?; do dd if=$i of=/dev/null bs=1M >>> count=10240 & done >>> iostat -k 10 >>> >>> >>> Halving the bus speed gives you a reasonable low >>> expectation of how >>> much data you should be able to pull of the disks. If your >>> disks can't >>> even fill half the bus bandwidth you certainly can cope >>> with more >>> disks or something is seriously wrong. >>> >>> MfG >>> Goswin > > Perfectly save. Just don't do it the other way around: > > !!!WARNING WRITE TEST!!! > > for i in /dev/sd?; do dd if=/dev/zero of=$i bs=1M count=10240 & done > iostat -k 10 Be advised: on some suse kernels /dev/zero is known to have a performance bug that would keep it from saturating a PCI-express bus. I think it was the kernel they had about a year ago (10.3 release). Greg -- Greg Freemyer Head of EDD Tape Extraction and Processing team Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- 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
