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i have a KVM linux based virtual machines, as the network performance of the host is running perfect with 1GB/s(in internal network) and using iperf tools it show that the network is running perfect in host , but guests is slow network performance as iperf result was so strange as it is not 100MB/s and is not 1GB/s its range between 350 and 500MB/s maximum, and this is result of using iperf command (iperf -c servername -P 15)

[ ID] Interval       Transfer     Bandwidth
[ 17]  0.0-10.0 sec  68.6 MBytes  57.5 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec  18.6 MBytes  15.5 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec  61.9 MBytes  51.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 11]  0.0-10.0 sec  16.0 MBytes  13.4 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 10]  0.0-10.0 sec  24.3 MBytes  20.4 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 15]  0.0-10.0 sec  20.2 MBytes  16.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 12]  0.0-10.0 sec  30.2 MBytes  25.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  36.2 MBytes  30.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  8]  0.0-10.0 sec  23.6 MBytes  19.8 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  9]  0.0-10.0 sec  24.2 MBytes  20.3 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 14]  0.0-10.0 sec  31.0 MBytes  25.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  7]  0.0-10.0 sec  16.6 MBytes  13.9 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  6]  0.0-10.0 sec  18.8 MBytes  15.7 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 13]  0.0-10.0 sec  13.3 MBytes  11.2 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[ 16]  0.0-10.0 sec  29.6 MBytes  24.8 Mbits/sec
[SUM]  0.0-10.0 sec    433 MBytes    363 Mbits/sec

i tested different network models and the best result was with the virtio model any one please can help to get the full performance of network and be 1 GB/s

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migrated from stackoverflow.com Feb 14 '13 at 14:24

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Dedicate a real/physical NIC to each of the your virtual machine, or use virtualization aware real/physical NIC, have a look at SR-IOV –  ydroneaud Feb 11 '13 at 10:11
    
@ydroneaud i did with another interface attached to another bridge , but the same result , as even when i run two machines in nat networking mode , it also runs with the same network speed. –  Moaz Refat Feb 11 '13 at 14:54
    
A dedicated real/physcal NIC is really dedicated using PCI passthrough: linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM docs.fedoraproject.org/en-US/Fedora/13/html/… –  ydroneaud Feb 11 '13 at 15:34
    
no one can advice ? –  Moaz Refat Feb 14 '13 at 10:17
    
@moaz-ferat move the question to serverfault.com –  ydroneaud Feb 14 '13 at 10:52
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