Greg, Yes, I did one very big like 100TB and I still see the regression. I even tried it with your extra dd option. I am wondering if the new kernel (2.6.36) introduced an options I need to set ? Can someone else try this? To reiterate the test scenario, Box 1, RHEL 5.1, stock kernel, dd bs=1024 count=1000000 if=/dev/zero bs=4096k of=/dev/null Box 2, RHEL 5.2, stock kernel,dd bs=1024 count=1000000 if=/dev/zero bs=4096k of=/dev/null Box 3, RHEL 5.3, stock kernel, dd bs=1024 count=1000000 if=/dev/zero bs=4096k of=/dev/null Box 4, RHEL 5.4, stock kernel, dd bs=1024 count=1000000 if=/dev/zero bs=4096k of=/dev/null Box 5, RHEL 5.4, 2.6.35, dd bs=1024 count=1000000 if=/dev/zero bs=4096k of=/dev/null Box 5 takes much much longer. And all of these boxes are the same model and specs... On Thu, Jan 20, 2011 at 9:29 AM, Greg Freemyer <greg.freemyer@xxxxxxxxx> wrote: > Mulyadi, > > You disappoint me. ;( > > Just kidding, but discussing dd throughput without the > "conv=fdatasync" parameter is just a waste of everyone's time. > > And Mag, use a big enough count that it at least takes a few seconds > to complete. ÂA tenth of a second or less is just way to short to use > as a benchmark. > > Greg > > On Thu, Jan 20, 2011 at 12:28 AM, Mulyadi Santosa > <mulyadi.santosa@xxxxxxxxx> wrote: >> Hi... >> >> On Thu, Jan 20, 2011 at 10:36, Mag Gam <magawake@xxxxxxxxx> wrote: >>> Running on Redhat 5.1 if I do, >> >> Are you sure you're using that archaic distro? Or are you talking >> about RHEL 5.1? >> >>> dd bs=1024 count=1000000 if=/dev/zero of=/dev/null >>> >>> I get around 30Gb/sec >> >> Hm, mine is: >> $ dd bs=1024 count=1000000 if=/dev/zero of=/dev/null >> 1000000+0 records in >> 1000000+0 records out >> 1024000000 bytes (1.0 GB) copied, 1.12169 seconds, 913 MB/s >> >> This is on 2.6.36 SMP kernel compiled with gcc version 4.1.2 20080704 >> (Red Hat 4.1.2-48). >> >>> >>> However, when I do this with 2.6.37 I get close to 5GB/sec >> >> what if you use another blocksize, let's say 4K or even 32K? here's >> mine (again): >> $ dd bs=4K count=1000000 if=/dev/zero of=/dev/null >> 1000000+0 records in >> 1000000+0 records out >> 4096000000 bytes (4.1 GB) copied, 1.31167 seconds, 3.1 GB/s >> >> $ dd bs=32K count=1000000 if=/dev/zero of=/dev/null >> 1000000+0 records in >> 1000000+0 records out >> 32768000000 bytes (33 GB) copied, 4.91775 seconds, 6.7 GB/s >> >> see the difference? >> >> IMHO it's a matter of what I call "block merge efficiency"....the more >> you stuff pages (that fits into a "magic" number), the faster I/O you >> got. >> >> -- >> regards, >> >> Mulyadi Santosa >> Freelance Linux trainer and consultant >> >> blog: the-hydra.blogspot.com >> training: mulyaditraining.blogspot.com >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > > > > -- > Greg Freemyer > Head of EDD Tape Extraction and Processing team > Litigation Triage Solutions Specialist > http://www.linkedin.com/in/gregfreemyer > CNN/TruTV Aired Forensic Imaging Demo - > ÂÂ http://insession.blogs.cnn.com/2010/03/23/how-computer-evidence-gets-retrieved/ > > The Norcross Group > The Intersection of Evidence & Technology > http://www.norcrossgroup.com > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
