Hi.. Udo, I am not sure I understood what you said. Did you mean that the 'dd' command also got cached in the osd node? or??
On Sun, Dec 11, 2016 at 10:46 PM, Udo Lembke <ulem...@polarzone.de> wrote: > 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 > >
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