On 8/13/2020 10:22 AM, Hean Seng wrote:
Hi
Cloudstack 4.14 , Advance Network with GiuestNetwork have Public IP
Create a compute offering with 10Mbps, but vm created stil able to burst to
200Mps
Any one know how to solve this
The virtualization hypervisor is responsible for enforcing network
limits. Which virtualization hypervisor are you using? Xen? KVM? VMware?
For KVM hosts, libvirt has the capability to throttle bandwidth. It has
three knobs for inbound and outbound bandwidth -- average bandwidth,
peak bandwidth, and burst number of bytes. To see the XML being
generated for your virtual machine, turn on debugging on the agent on
one of your hosts in /etc/cloudstack/agent/log4j-cloud.xml (change all
INFO to DEBUG then restart the agent), then start the instance on that
specific host. Then look for the XML in the log file in
/var/log/cloudstack/agent/agent.log which should have a segment in it
like this for the network interface: [note -- all file locations are for
CentOS 7]
...
*<bandwidth> <inbound average='1000' peak='5000' burst='5120'/>
<outbound average='128' peak='256' burst='256'/> </bandwidth> ... *
For information on what that means:
https://libvirt.org/formatnetwork.html#elementQoS
Hmm, yeah, just checked the source.
if ((s_libvirtVersion >= 9004) && (_networkRateKBps > 0)) {// supported from libvirt 0.9.4
netBuilder.append("<bandwidth>\n");
netBuilder.append("<inbound average='" +_networkRateKBps +"' peak='" +_networkRateKBps
+"'/>\n");
netBuilder.append("<outbound average='" +_networkRateKBps +"' peak='" +_networkRateKBps
+"'/>\n");
netBuilder.append("</bandwidth>\n");
}
According to the source code, average and peak for both inbound and
outbound are set to the max bandwidth in the offering, while 'burst' is
not defined. Note the limitation documented in the above libvirt
document: the 'peak' is ignored in the outbound setting, because of
Linux OS network layer limitations. Cloudstack properly produces the
tag, but the KVM hypervisor ignores it. If the hypervisor ever actually
respects the limit Cloudstack is sending it the right data, but
Cloudstack can't force the hypervisor to do something it can't currently do.
In other words, the behavior you're seeing appears to be a result of
limitations of KVM on Linux if that's the hypervisor you're using.
Apparently only the 'average' is respected for outbound data traffic,
meaning you'll be able to burst on outbound traffic and it'll be
throttled only once the average exceeds the limit.
