On 21-3-2018 13:47, Paul Emmerich wrote: > Hi, > > 2.3µs is a typical delay for a 10GBASE-T connection. But fiber or SFP+ > DAC connections should be faster: switches are typically in the range of > ~500ns to 1µs. > > > But you'll find that this small difference in latency induced by the > switch will be quite irrelevant in the grand scheme of things when using > the Linux network stack... But I think it does when people start to worry about selecting High clock speed CPUS versus packages with more cores... 900ns is quite a lot if you have that mindset. And probably 1800ns at that, because the delay will be a both ends. Or perhaps even 3600ns because the delay is added at every ethernet connector??? But I'm inclined to believe you that the network stack could take quite some time... --WjW > Paul > > 2018-03-21 12:16 GMT+01:00 Willem Jan Withagen <wjw@xxxxxxxxxxx > <mailto:wjw@xxxxxxxxxxx>>: > > Hi, > > I just ran into this table for a 10G Netgear switch we use: > > Fiberdelays: > 10 Gbps vezelvertraging (64 bytepakketten): 1.827 µs > 10 Gbps vezelvertraging (512 bytepakketten): 1.919 µs > 10 Gbps vezelvertraging (1024 bytepakketten): 1.971 µs > 10 Gbps vezelvertraging (1518 bytepakketten): 1.905 µs > > Copperdelays: > 10 Gbps kopervertraging (64 bytepakketten): 2.728 µs > 10 Gbps kopervertraging (512 bytepakketten): 2.85 µs > 10 Gbps kopervertraging (1024 bytepakketten): 2.904 µs > 10 Gbps kopervertraging (1518 bytepakketten): 2.841 µs > > Fiberdelays: > 1 Gbps vezelvertraging (64 bytepakketten) 2.289 µs > 1 Gbps vezelvertraging (512 bytepakketten) 2.393 µs > 1 Gbps vezelvertraging (1024 bytepakketten) 2.423 µs > 1 Gbps vezelvertraging (1518 bytepakketten) 2.379 µs > > Copperdelays: > 1 Gbps kopervertraging (64 bytepakketten) 2.707 µs > 1 Gbps kopervertraging (512 bytepakketten) 2.821 µs > 1 Gbps kopervertraging (1024 bytepakketten) 2.866 µs > 1 Gbps kopervertraging (1518 bytepakketten) 2.826 µs > > So the difference is serious: 900ns on a total of 1900ns for a 10G > pakket. > Other strange thing is that 1K packets are slower than 1518 bytes. > > So that might warrant connecting boxes preferably with optics > instead of CAT cableing if you are trying to squeeze the max out of > a setup. > > Sad thing is that they do not report for jumbo frames, and doing these > measurements your self is not easy... > > --WjW > > _______________________________________________ > 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> > > > > > -- > -- > Paul Emmerich > > croit GmbH > Freseniusstr. 31h > 81247 München > www.croit.io <http://www.croit.io> > Tel: +49 89 1896585 90 _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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