On Thu, Mar 21, 2013 at 8:27 PM, Anders Henke <anders.he...@1und1.de> wrote: > In some areas, the performance impact by virtualization is dramatically > high (especially in networking), in others the performance impact > (cpu-intensive tasks like calculation) it can be as low as 3-5%. > As a rule of thumb, most kind of virtualization result in 10-20% of > overall performance loss, which fits your "12.5%" fairly well. >
But after I increased the users, I can got 12000/min with direct access, LVS-DR could not, is is normal ? > The virtualization layer does add some latency to your network. While > the overall amount may look low, compare it to the usual latency on your > network and you may experience an overall roundtrip increase of 200%. > > If you're putting a virtualized load balancer in front of this, > you'll add not only the "natural" latency but also the extra > latency by the virtualization layer - so in the end, the latency > from a hardware client via VM-loadbalancer to VM-realserver may be > 3-4 times as high as a hardware client accessing a hardware realserver. > So for transactions on short lived tcp connection, large roundtrip can not achieve high performance, right ? > Another point is CPU overcommitment: adding more virtual cores to a > server doesn't necessarily increase the performance, it may also worsen > performance. You've assigned 8*4 cores for the real servers and 2 more > cores for the loadbalancer. The x7550 does offer 8 real cores, so set > aside one core just for the virtualization layer and management, your > hypervisor has around 7 cores to spend. > My test machine have 2 X7550 CPU, total 16 cores, 32 threads, when I use 32 virtual cores, and 2 virtual cores which assign to loadbalancer is near idle, it should not be overcommitment, right ? > > My advice: > -test the performance of accessing all VMs in parallel without using the > loadbalancer. If your application is not sensitive to network latency, > the result shouldn't be very far from your current results and > probably a little better (as you're reducing network latency). > -do assign less CPU cores to each VM to reduce the overall hypervisor > switching overhead, test again. The performance should improve a lot. > -if network latency is an issue, do put your balancer on "real" hardware. > Very good advice, thank you very much! -- Dongsheng > > > Anders > -- > 1&1 Internet AG Expert Systems Architect (IT Operations) > Brauerstrasse 50 v://49.721.91374.0 > D-76135 Karlsruhe f://49.721.91374.225 > > Amtsgericht Montabaur HRB 6484 > Vorstände: Henning Ahlert, Ralph Dommermuth, Matthias Ehrlich, > Robert Hoffmann, Andreas Hofmann, Markus Huhn, Hans-Henning Kettler, > Dr. Oliver Mauss, Jan Oetjen, Martin Witt, Christian Würst > Aufsichtsratsvorsitzender: Michael Scheeren > _______________________________________________ Please read the documentation before posting - it's available at: http://www.linuxvirtualserver.org/ LinuxVirtualServer.org mailing list - lvs-users@LinuxVirtualServer.org Send requests to lvs-users-requ...@linuxvirtualserver.org or go to http://lists.graemef.net/mailman/listinfo/lvs-users
