Someone could get a performance throughput on RBD of 600MB/s or more on (rw) with a block size of 32768k? German Anders Field Storage Support Engineer Despegar.com - IT Team > --- Original message --- > Asunto: Re: Slow IOPS on RBD compared to journal and > backingdevices > De: Christian Balzer <chibi at gol.com> > Para: Josef Johansson <josef at oderland.se> > Cc: <ceph-users at lists.ceph.com> > Fecha: Wednesday, 14/05/2014 09:33 > > > Hello! > > On Wed, 14 May 2014 11:29:47 +0200 Josef Johansson wrote: > >> >> Hi Christian, >> >> I missed this thread, haven't been reading the list that well the last >> weeks. >> >> You already know my setup, since we discussed it in an earlier thread. >> I >> don't have a fast backing store, but I see the slow IOPS when doing >> randwrite inside the VM, with rbd cache. Still running dumpling here >> though. >> > Nods, I do recall that thread. > >> >> A thought struck me that I could test with a pool that consists of >> OSDs >> that have tempfs-based disks, think I have a bit more latency than >> your >> IPoIB but I've pushed 100k IOPS with the same network devices before. >> This would verify if the problem is with the journal disks. I'll also >> try to run the journal devices in tempfs as well, as it would test >> purely Ceph itself. >> > That would be interesting indeed. > Given what I've seen (with the journal at 20% utilization and the > actual > filestore ataround 5%) I'd expect Ceph to be the culprit. > >> >> I'll get back to you with the results, hopefully I'll manage to get >> them >> done during this night. >> > Looking forward to that. ^^ > > > Christian >> >> Cheers, >> Josef >> >> On 13/05/14 11:03, Christian Balzer wrote: >>> >>> I'm clearly talking to myself, but whatever. >>> >>> For Greg, I've played with all the pertinent journal and filestore >>> options and TCP nodelay, no changes at all. >>> >>> Is there anybody on this ML who's running a Ceph cluster with a fast >>> network and FAST filestore, so like me with a big HW cache in front of >>> a RAID/JBODs or using SSDs for final storage? >>> >>> If so, what results do you get out of the fio statement below per OSD? >>> In my case with 4 OSDs and 3200 IOPS that's about 800 IOPS per OSD, >>> which is of course vastly faster than the normal indvidual HDDs could >>> do. >>> >>> So I'm wondering if I'm hitting some inherent limitation of how fast a >>> single OSD (as in the software) can handle IOPS, given that everything >>> else has been ruled out from where I stand. >>> >>> This would also explain why none of the option changes or the use of >>> RBD caching has any measurable effect in the test case below. >>> As in, a slow OSD aka single HDD with journal on the same disk would >>> clearly benefit from even the small 32MB standard RBD cache, while in >>> my test case the only time the caching becomes noticeable is if I >>> increase the cache size to something larger than the test data size. >>> ^o^ >>> >>> On the other hand if people here regularly get thousands or tens of >>> thousands IOPS per OSD with the appropriate HW I'm stumped. >>> >>> Christian >>> >>> On Fri, 9 May 2014 11:01:26 +0900 Christian Balzer wrote: >>> >>>> >>>> On Wed, 7 May 2014 22:13:53 -0700 Gregory Farnum wrote: >>>> >>>>> >>>>> Oh, I didn't notice that. I bet you aren't getting the expected >>>>> throughput on the RAID array with OSD access patterns, and that's >>>>> applying back pressure on the journal. >>>>> >>>> In the a "picture" being worth a thousand words tradition, I give you >>>> this iostat -x output taken during a fio run: >>>> >>>> avg-cpu: %user %nice %system %iowait %steal %idle >>>> 50.82 0.00 19.43 0.17 0.00 29.58 >>>> >>>> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s >>>> avgrq-sz avgqu-sz await r_await w_await svctm %util >>>> sda 0.00 51.50 0.00 1633.50 0.00 7460.00 >>>> 9.13 0.18 0.11 0.00 0.11 0.01 1.40 sdb >>>> 0.00 0.00 0.00 1240.50 0.00 5244.00 8.45 0.30 >>>> 0.25 0.00 0.25 0.02 2.00 sdc 0.00 5.00 >>>> 0.00 2468.50 0.00 13419.00 10.87 0.24 0.10 0.00 >>>> 0.10 0.09 22.00 sdd 0.00 6.50 0.00 1913.00 >>>> 0.00 10313.00 10.78 0.20 0.10 0.00 0.10 0.09 16.60 >>>> >>>> The %user CPU utilization is pretty much entirely the 2 OSD processes, >>>> note the nearly complete absence of iowait. >>>> >>>> sda and sdb are the OSDs RAIDs, sdc and sdd are the journal SSDs. >>>> Look at these numbers, the lack of queues, the low wait and service >>>> times (this is in ms) plus overall utilization. >>>> >>>> The only conclusion I can draw from these numbers and the network >>>> results below is that the latency happens within the OSD processes. >>>> >>>> Regards, >>>> >>>> Christian >>>>> >>>>> When I suggested other tests, I meant with and without Ceph. One >>>>> particular one is OSD bench. That should be interesting to try at a >>>>> variety of block sizes. You could also try runnin RADOS bench and >>>>> smalliobench at a few different sizes. >>>>> -Greg >>>>> >>>>> On Wednesday, May 7, 2014, Alexandre DERUMIER <aderumier at odiso.com> >>>>> wrote: >>>>> >>>>>> >>>>>> Hi Christian, >>>>>> >>>>>> Do you have tried without raid6, to have more osd ? >>>>>> (how many disks do you have begin the raid6 ?) >>>>>> >>>>>> >>>>>> Aslo, I known that direct ios can be quite slow with ceph, >>>>>> >>>>>> maybe can you try without --direct=1 >>>>>> >>>>>> and also enable rbd_cache >>>>>> >>>>>> ceph.conf >>>>>> [client] >>>>>> rbd cache = true >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> ----- Mail original ----- >>>>>> >>>>>> De: "Christian Balzer" <chibi at gol.com <javascript:;>> >>>>>> ?: "Gregory Farnum" <greg at inktank.com <javascript:;>>, >>>>>> ceph-users at lists.ceph.com <javascript:;> >>>>>> Envoy?: Jeudi 8 Mai 2014 04:49:16 >>>>>> Objet: Re: Slow IOPS on RBD compared to journal and >>>>>> backing devices >>>>>> >>>>>> On Wed, 7 May 2014 18:37:48 -0700 Gregory Farnum wrote: >>>>>> >>>>>>> >>>>>>> On Wed, May 7, 2014 at 5:57 PM, Christian Balzer >>>>>>> <chibi at gol.com<javascript:;>> >>>>>> wrote: >>>>>>> >>>>>>>> >>>>>>>> Hello, >>>>>>>> >>>>>>>> ceph 0.72 on Debian Jessie, 2 storage nodes with 2 OSDs each. The >>>>>>>> journals are on (separate) DC 3700s, the actual OSDs are RAID6 >>>>>>>> behind an Areca 1882 with 4GB of cache. >>>>>>>> >>>>>>>> Running this fio: >>>>>>>> >>>>>>>> fio --size=400m --ioengine=libaio --invalidate=1 --direct=1 >>>>>>>> --numjobs=1 --rw=randwrite --name=fiojob --blocksize=4k >>>>>>>> --iodepth=128 >>>>>>>> >>>>>>>> results in: >>>>>>>> >>>>>>>> 30k IOPS on the journal SSD (as expected) >>>>>>>> 110k IOPS on the OSD (it fits neatly into the cache, no surprise >>>>>>>> there) 3200 IOPS from a VM using userspace RBD >>>>>>>> 2900 IOPS from a host kernelspace mounted RBD >>>>>>>> >>>>>>>> When running the fio from the VM RBD the utilization of the >>>>>>>> journals is about 20% (2400 IOPS) and the OSDs are bored at 2% >>>>>>>> (1500 IOPS after some obvious merging). >>>>>>>> The OSD processes are quite busy, reading well over 200% on atop, >>>>>>>> but the system is not CPU or otherwise resource starved at that >>>>>>>> moment. >>>>>>>> >>>>>>>> Running multiple instances of this test from several VMs on >>>>>>>> different hosts changes nothing, as in the aggregated IOPS for >>>>>>>> the whole cluster will still be around 3200 IOPS. >>>>>>>> >>>>>>>> Now clearly RBD has to deal with latency here, but the network is >>>>>>>> IPoIB with the associated low latency and the journal SSDs are >>>>>>>> the (consistently) fasted ones around. >>>>>>>> >>>>>>>> I guess what I am wondering about is if this is normal and to be >>>>>>>> expected or if not where all that potential performance got lost. >>>>>>> Hmm, with 128 IOs at a time (I believe I'm reading that correctly?) >>>>>> Yes, but going down to 32 doesn't change things one iota. >>>>>> Also note the multiple instances I mention up there, so that would >>>>>> be 256 IOs at a time, coming from different hosts over different >>>>>> links and nothing changes. >>>>>> >>>>>>> >>>>>>> that's about 40ms of latency per op (for userspace RBD), which >>>>>>> seems awfully long. You should check what your client-side objecter >>>>>>> settings are; it might be limiting you to fewer outstanding ops >>>>>>> than that. >>>>>> Googling for client-side objecter gives a few hits on ceph devel and >>>>>> bugs and nothing at all as far as configuration options are >>>>>> concerned. Care to enlighten me where one can find those? >>>>>> >>>>>> Also note the kernelspace (3.13 if it matters) speed, which is very >>>>>> much in the same (junior league) ballpark. >>>>>> >>>>>>> >>>>>>> If >>>>>>> it's available to you, testing with Firefly or even master would be >>>>>>> interesting ? there's some performance work that should reduce >>>>>>> latencies. >>>>>>> >>>>>> Not an option, this is going into production next week. >>>>>> >>>>>>> >>>>>>> But a well-tuned (or even default-tuned, I thought) Ceph cluster >>>>>>> certainly doesn't require 40ms/op, so you should probably run a >>>>>>> wider array of experiments to try and figure out where it's coming >>>>>>> from. >>>>>> I think we can rule out the network, NPtcp gives me: >>>>>> --- >>>>>> 56: 4096 bytes 1546 times --> 979.22 Mbps in 31.91 usec >>>>>> --- >>>>>> >>>>>> For comparison at about 512KB it reaches maximum throughput and >>>>>> still isn't that laggy: >>>>>> --- >>>>>> 98: 524288 bytes 121 times --> 9700.57 Mbps in 412.35 usec >>>>>> --- >>>>>> >>>>>> So with the network performing as well as my lengthy experience with >>>>>> IPoIB led me to believe, what else is there to look at? >>>>>> The storage nodes perform just as expected, indicated by the local >>>>>> fio tests. >>>>>> >>>>>> That pretty much leaves only Ceph/RBD to look at and I'm not really >>>>>> sure what experiments I should run on that. ^o^ >>>>>> >>>>>> Regards, >>>>>> >>>>>> Christian >>>>>> >>>>>>> >>>>>>> -Greg >>>>>>> Software Engineer #42 @ http://inktank.com | http://ceph.com >>>>>>> >>>>>> >>>>>> -- >>>>>> Christian Balzer Network/Systems Engineer >>>>>> chibi at gol.com <javascript:;> Global OnLine Japan/Fusion >>>>>> Communications http://www.gol.com/ >>>>>> _______________________________________________ >>>>>> ceph-users mailing list >>>>>> ceph-users at lists.ceph.com <javascript:;> >>>>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>>>> >>>>> >>>> >>> >> >> _______________________________________________ >> ceph-users mailing list >> ceph-users at lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > -- > Christian Balzer Network/Systems Engineer > chibi at gol.com Global OnLine Japan/Fusion Communications > http://www.gol.com/ > _______________________________________________ > ceph-users mailing list > ceph-users at lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -------------- next part -------------- An HTML attachment was scrubbed... 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