Hi, but I assume you measure also cache in this scenario - the osd-nodes has cached the writes in the filebuffer (due this the latency should be very small).
Udo On 12.12.2016 03:00, V Plus wrote: > Thanks Somnath! > As you recommended, I executed: > dd if=/dev/zero bs=1M count=4096 of=/dev/rbd0 > dd if=/dev/zero bs=1M count=4096 of=/dev/rbd1 > > Then the output results look more reasonable! > Could you tell me why?? > > Btw, the purpose of my run is to test the performance of rbd in ceph. > Does my case mean that before every test, I have to "initialize" all > the images??? > > Great thanks!! > > On Sun, Dec 11, 2016 at 8:47 PM, Somnath Roy <somnath....@sandisk.com > <mailto:somnath....@sandisk.com>> wrote: > > Fill up the image with big write (say 1M) first before reading and > you should see sane throughput. > > > > Thanks & Regards > > Somnath > > *From:*ceph-users [mailto:ceph-users-boun...@lists.ceph.com > <mailto:ceph-users-boun...@lists.ceph.com>] *On Behalf Of *V Plus > *Sent:* Sunday, December 11, 2016 5:44 PM > *To:* ceph-users@lists.ceph.com <mailto:ceph-users@lists.ceph.com> > *Subject:* [ceph-users] Ceph performance is too good (impossible..)... > > > > Hi Guys, > > we have a ceph cluster with 6 machines (6 OSD per host). > > 1. I created 2 images in Ceph, and map them to another host A > (*/outside /*the Ceph cluster). On host A, I > got *//dev/rbd0/* and*/ /dev/rbd1/*. > > 2. I start two fio job to perform READ test on rbd0 and rbd1. (fio > job descriptions can be found below) > > */"sudo fio fioA.job -output a.txt & sudo fio fioB.job -output > b.txt & wait"/* > > 3. After the test, in a.txt, we got */bw=1162.7MB/s/*, in b.txt, > we get */bw=3579.6MB/s/*. > > The results do NOT make sense because there is only one NIC on > host A, and its limit is 10 Gbps (1.25GB/s). > > > > I suspect it is because of the cache setting. > > But I am sure that in file *//etc/ceph/ceph.conf/* on host A,I > already added: > > */[client]/* > > */rbd cache = false/* > > > > Could anyone give me a hint what is missing? why.... > > Thank you very much. > > > > *fioA.job:* > > /[A]/ > > /direct=1/ > > /group_reporting=1/ > > /unified_rw_reporting=1/ > > /size=100%/ > > /time_based=1/ > > /filename=/dev/rbd0/ > > /rw=read/ > > /bs=4MB/ > > /numjobs=16/ > > /ramp_time=10/ > > /runtime=20/ > > > > *fioB.job:* > > /[B]/ > > /direct=1/ > > /group_reporting=1/ > > /unified_rw_reporting=1/ > > /size=100%/ > > /time_based=1/ > > /filename=/dev/rbd1/ > > /rw=read/ > > /bs=4MB/ > > /numjobs=16/ > > /ramp_time=10/ > > /runtime=20/ > > > > /Thanks.../ > > PLEASE NOTE: The information contained in this electronic mail > message is intended only for the use of the designated > recipient(s) named above. If the reader of this message is not the > intended recipient, you are hereby notified that you have received > this message in error and that any review, dissemination, > distribution, or copying of this message is strictly prohibited. > If you have received this communication in error, please notify > the sender by telephone or e-mail (as shown above) immediately and > destroy any and all copies of this message in your possession > (whether hard copies or electronically stored copies). > > > > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
