I believe, that is due to bio vs request. LVM/DM block devices receive and use bio requests where as sdX uses requests (which are coalesced from these bio's using elevator algorithms). So the actual disk transactions would be fewer. --Malahal. unlisted [unlisted@gmail.com] wrote: > Why would I see 50x the amount of transactions on the lvm volume vs the > actual underlying block device ? > > avg-cpu: %user %nice %system %iowait %steal %idle > 0.00 0.00 11.41 57.07 0.00 31.51 > Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn > sda 211.33 0.00 56.12 0 113 > sdb 268.47 63.05 0.00 128 0 > dm-0 14365.52 0.00 56.11 0 113 > dm-1 0.00 0.00 0.00 0 0 > sdc 0.00 0.00 0.00 0 0 > 211 tps versus 14365 tps. The box is idle and the following command was > running: > > dd if=/dev/sdb of=/home/xxxxxxx/bigrandomfile.txt bs=4k count=10000000 > Sam > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/