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Slow network speed inside CT [message #52832]

Fri, 12 May 2017 22:55

creiss
Messages: 7
Registered: February 2015
Location: Germany

Junior Member

Hey folks,

I am running OpenVZ Distribution 7 (yum updated to latest). I am observing some weird abnormaliy: If I run a freshly installed VM and download something from a fast enough mirror I usually average around 800mbit/s. If I run the same download from the same mirrors from inside a freshly spawned CT I am averaged at around 100mbit/s. All CT/VMs are Centos7, with no modifications to either the OpenVZ Node nor to either CT nor VM.

Recreating either CT/VM will yield same results. Writing into a tmpfs mount to rule out the disk IO does only marginaly affect the results. CPUs ( Cool

are idle. The OpenVZ node is empty, no other machine is running (not yet productive).

I am in both cases (ct/vm) using routed with a 10.7.0.0/24 network routing through my OpenVZ with does NATing:

iptables -t nat -A POSTROUTING -o br0 -s 10.7.0.0/24 -j SNAT --to-source 1.2.3.4

I am adding network configuration to CT with

prlc ${prl_bin} set ${_arg_name} --iface venet0 --ipadd ${_arg_ip}

and to VMs with

${prl_bin} set ${_arg_name} --device-del net0
${prl_bin} set ${_arg_name} --device-add net --type routed --ipadd ${_arg_ip}

I am out of my wits; something makes the CT really really crawl when everything else is pretty much identical.
Any clue is greatly appreciated!
-Chris

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