Hi.. Udo,
I am not sure I understood what you said.On Sun, Dec 11, 2016 at 10:46 PM, Udo Lembke <ulembke@xxxxxxxxxxxx> 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.Roy@xxxxxxxxxxx
> <mailto:Somnath.Roy@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-bounces@lists.ceph.com
> <mailto:ceph-users-bounces@lists.ceph.com >] *On Behalf Of *V Plus
> *Sent:* Sunday, December 11, 2016 5:44 PM
> *To:* ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxx.com >
> *Subject:* 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.../
>
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