On 26-6-2017 09:01, Christian Wuerdig wrote: > Well, preferring faster clock CPUs for SSD scenarios has been floated > several times over the last few months on this list. And realistic or > not, Nick's and Kostas' setup are similar enough (testing single disk) > that it's a distinct possibility. > Anyway, as mentioned measuring the performance counters would probably > provide more insight. I read the advise as: prefer GHz over cores. And especially since there is a sort of balance between either GHz or cores, that can be an expensive one. Getting both means you have to pay relatively substantial more money. And for an average Ceph server with plenty OSDs, I personally just don't buy that. There you'd have to look at the total throughput of the the system, and latency is only one of the many factors. Let alone in a cluster with several hosts (and or racks). There the latency is dictated by the network. So a bad choice of network card or switch will out do any extra cycles that your CPU can burn. I think that just testing 1 OSD is testing artifacts, and has very little to do with running an actual ceph cluster. So if one would like to test this, the test setup should be something like: 3 hosts with something like 3 disks per host, min_disk=2 and a nice workload. Then turn the GHz-knob and see what happens with client latency and throughput. --WjW > On Sun, Jun 25, 2017 at 4:53 AM, Willem Jan Withagen <wjw@xxxxxxxxxxx > <mailto:wjw@xxxxxxxxxxx>> wrote: > > > > Op 24 jun. 2017 om 14:17 heeft Maged Mokhtar <mmokhtar@xxxxxxxxxxx > <mailto:mmokhtar@xxxxxxxxxxx>> het volgende geschreven: > >> My understanding was this test is targeting latency more than >> IOPS. This is probably why its was run using QD=1. It also makes >> sense that cpu freq will be more important than cores. >> > > But then it is not generic enough to be used as an advise! > It is just a line in 3D-space. > As there are so many > > --WjW > >> On 2017-06-24 12:52, Willem Jan Withagen wrote: >> >>> On 24-6-2017 05:30, Christian Wuerdig wrote: >>>> The general advice floating around is that your want CPUs with high >>>> clock speeds rather than more cores to reduce latency and >>>> increase IOPS >>>> for SSD setups (see also >>>> http://www.sys-pro.co.uk/ceph-storage-fast-cpus-ssd-performance/ >>>> <http://www.sys-pro.co.uk/ceph-storage-fast-cpus-ssd-performance/>) >>>> So >>>> something like a E5-2667V4 might bring better results in that >>>> situation. >>>> Also there was some talk about disabling the processor C states >>>> in order >>>> to bring latency down (something like this should be easy to test: >>>> https://stackoverflow.com/a/22482722/220986 >>>> <https://stackoverflow.com/a/22482722/220986>) >>> >>> I would be very careful to call this a general advice... >>> >>> Although the article is interesting, it is rather single sided. >>> >>> The only thing is shows that there is a lineair relation between >>> clockspeed and write or read speeds??? >>> The article is rather vague on how and what is actually tested. >>> >>> By just running a single OSD with no replication a lot of the >>> functionality is left out of the equation. >>> Nobody is running just 1 osD on a box in a normal cluster host. >>> >>> Not using a serious SSD is another source of noise on the conclusion. >>> More Queue depth can/will certainly have impact on concurrency. >>> >>> I would call this an observation, and nothing more. >>> >>> --WjW >>>> >>>> On Sat, Jun 24, 2017 at 1:28 AM, Kostas Paraskevopoulos >>>> <reverend.x3@xxxxxxxxx <mailto:reverend.x3@xxxxxxxxx> >>>> <mailto:reverend.x3@xxxxxxxxx <mailto:reverend.x3@xxxxxxxxx>>> >>>> wrote: >>>> >>>> Hello, >>>> >>>> We are in the process of evaluating the performance of a testing >>>> cluster (3 nodes) with ceph jewel. Our setup consists of: >>>> 3 monitors (VMs) >>>> 2 physical servers each connected with 1 JBOD running Ubuntu >>>> Server >>>> 16.04 >>>> >>>> Each server has 32 threads @2.1GHz and 128GB RAM. >>>> The disk distribution per server is: >>>> 38 * HUS726020ALS210 (SAS rotational) >>>> 2 * HUSMH8010BSS200 (SAS SSD for journals) >>>> 2 * ST1920FM0043 (SAS SSD for data) >>>> 1 * INTEL SSDPEDME012T4 (NVME measured with fio ~300K iops) >>>> >>>> Since we don't currently have a 10Gbit switch, we test the >>>> performance >>>> with the cluster in a degraded state, the noout flag set and >>>> we mount >>>> rbd images on the powered on osd node. We confirmed that the >>>> network >>>> is not saturated during the tests. >>>> >>>> We ran tests on the NVME disk and the pool created on this >>>> disk where >>>> we hoped to get the most performance without getting limited >>>> by the >>>> hardware specs since we have more disks than CPU threads. >>>> >>>> The nvme disk was at first partitioned with one partition >>>> and the >>>> journal on the same disk. The performance on random 4K reads was >>>> topped at 50K iops. We then removed the osd and partitioned >>>> with 4 >>>> data partitions and 4 journals on the same disk. The performance >>>> didn't increase significantly. Also, since we run read >>>> tests, the >>>> journals shouldn't cause performance issues. >>>> >>>> We then ran 4 fio processes in parallel on the same rbd >>>> mounted image >>>> and the total iops reached 100K. More parallel fio processes >>>> didn't >>>> increase the measured iops. >>>> >>>> Our ceph.conf is pretty basic (debug is set to 0/0 for >>>> everything) and >>>> the crushmap just defines the different buckets/rules for >>>> the disk >>>> separation (rotational, ssd, nvme) in order to create the >>>> required >>>> pools >>>> >>>> Is the performance of 100.000 iops for random 4K read normal >>>> for a >>>> disk that on the same benchmark runs at more than 300K iops >>>> on the >>>> same hardware or are we missing something? >>>> >>>> Best regards, >>>> Kostas >>>> _______________________________________________ >>>> ceph-users mailing list >>>> ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> >>>> <mailto:ceph-users@xxxxxxxxxxxxxx >>>> <mailto:ceph-users@xxxxxxxxxxxxxx>> >>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> >>>> <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> ceph-users mailing list >>>> ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> >>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> >>>> >>> >>> _______________________________________________ >>> ceph-users mailing list >>> ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> <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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