Hi, I found something similar awhile ago within a VM. http://lists.opennebula.org/pipermail/ceph-users-ceph.com/2014-November/045034.html I don't know if the change suggested by Ilya ever got applied. Cheers, Dan On Wed, Jun 10, 2015 at 1:47 PM, Nick Fisk <nick@xxxxxxxxxx> wrote: > Hi, > > Using Kernel RBD client with Kernel 4.03 (I have also tried some older > kernels with the same effect) and IO is being split into smaller IO's which > is having a negative impact on performance. > > cat /sys/block/sdc/queue/max_hw_sectors_kb > 4096 > > cat /sys/block/rbd0/queue/max_sectors_kb > 4096 > > Using DD > dd if=/dev/rbd0 of=/dev/null bs=4M > > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz > avgqu-sz await r_await w_await svctm %util > rbd0 0.00 0.00 201.50 0.00 25792.00 0.00 256.00 > 1.99 10.15 10.15 0.00 4.96 100.00 > > > Using FIO with 4M blocks > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz > avgqu-sz await r_await w_await svctm %util > rbd0 0.00 0.00 232.00 0.00 118784.00 0.00 1024.00 > 11.29 48.58 48.58 0.00 4.31 100.00 > > Any ideas why IO sizes are limited to 128k (256 blocks) in DD's case and > 512k in Fio's case? > > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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