On Thu, Sep 10, 2015 at 10:36 PM, Jan Schermer <j...@schermer.cz> wrote:
> > On 10 Sep 2015, at 16:26, Haomai Wang <haomaiw...@gmail.com> wrote: > > Actually we can reach 700us per 4k write IO for single io depth(2 copy, > E52650, 10Gib, intel s3700). So I think 400 read iops shouldn't be a > unbridgeable problem. > > > Flushed to disk? > of course > > > CPU is critical for ssd backend, so what's your cpu model? > > On Thu, Sep 10, 2015 at 9:48 PM, Jan Schermer <j...@schermer.cz> wrote: > >> It's certainly not a problem with DRBD (yeah, it's something completely >> different but it's used for all kinds of workloads including things like >> replicated tablespaces for databases). >> It won't be a problem with VSAN (again, a bit different, but most people >> just want something like that) >> It surely won't be a problem with e.g. ScaleIO which should be comparable >> to Ceph. >> >> Latency on the network can be very low (0.05ms on my 10GbE). Latency on >> good SSDs is 2 orders of magnitute lower (as low as 0.00005 ms). Linux is >> pretty good nowadays at waking up threads and pushing the work. Multiply >> those numbers by whatever factor and it's still just a fraction of the >> 0.5ms needed. >> The problem is quite frankly slow OSD code and the only solution now is >> to keep the data closer to the VM. >> >> Jan >> >> > On 10 Sep 2015, at 15:38, Gregory Farnum <gfar...@redhat.com> wrote: >> > >> > On Thu, Sep 10, 2015 at 2:34 PM, Stefan Priebe - Profihost AG >> > <s.pri...@profihost.ag> wrote: >> >> Hi, >> >> >> >> while we're happy running ceph firefly in production and also reach >> >> enough 4k read iop/s for multithreaded apps (around 23 000) with qemu >> 2.2.1. >> >> >> >> We've now a customer having a single threaded application needing >> around >> >> 2000 iop/s but we don't go above 600 iop/s in this case. >> >> >> >> Any tuning hints for this case? >> > >> > If the application really wants 2000 sync IOPS to disk without any >> > parallelism, I don't think any network storage system is likely to >> > satisfy him — that's only half a millisecond per IO. 600 IOPS is about >> > the limit of what the OSD can do right now (in terms of per-op >> > speeds), and although there is some work being done to improve that >> > it's not going to be in a released codebase for a while. >> > >> > Or perhaps I misunderstood the question? >> > _______________________________________________ >> > 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 >> > > > > -- > > Best Regards, > > Wheat > > > -- Best Regards, Wheat
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