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Re: [Xen-users] XCP bandwidth management

  • To: Alexandre Bezroutchko <abb@xxxxxxxxx>
  • From: "msgbox450@xxxxxxxxx" <msgbox450@xxxxxxxxx>
  • Date: Mon, 23 May 2011 11:53:59 +0100
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 23 May 2011 03:55:13 -0700
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Ah, nice to know I am not the only one with this problem. 

I didn't actually test the XCP bandwidth limit either...I just assumed it worked because it didn't give an error, perhaps you are right about it silently doing nothing. I guess that is a feature request for the XCP devs then if it doesn't?

Do you know of any better documentation for the ovs-vsctl? Maybe there is an answer there but I can't seem to find a full syntax explanation :(

For the sFlow collector, it's one we wrote ourselves...not really too sure it's working right though because we seem to get multiple readings for the same interface. Also, not sure how to stop it being easily floodable (sFlow would be in a domU so if another domU floods it with these sFlow packets it would screw up the results I guess). Even if it works, not sure how useful it is...  it only tells us what's been used, we'd still need the rate limiter thing to work.

I guess the ideal solution for me would be to have a VM guest that logs all the traffic, does some calculations. I want to check if the VM is averaging too fast across the month to meet its monthly target, and if it is,slow it down until the target is met (using 95 percentile perhaps to ignore spikes of activity).

Really don't know how to achieve that with what's available :(

On Sun, May 22, 2011 at 9:39 PM, Alexandre Bezroutchko <abb@xxxxxxxxx> wrote:

1 - Limit the interface using the XenCenter GUI..
I believe in free version of XenServer bandwidth limiting does not work (it silently does nothing), I doubt this feature is enabled in XCP, have you tried?

I have patched /etc/xensource/scripts/vif script to (among other things) call ovs-vsctl to set ingress policy rate. I imagine commercial edition of XenServer do pretty much the same. Downside is that this approach only limits traffic from VM. If you are billed for traffic your VMs download from the Internet (like I am), this is not enough.

I've tried to play with 'tc' to limit traffic in another direction, but it never worked properly -- I want to cap the rate to 10Mbps, but it always gave me below 1Mbps whatever I do.

2 - Use sFlow in XCP to capture the data. Well this works for looking at how much bandwidth they are using, but I haven't found any existing tool that
will act on that data to do traffic shaping.
I have tried this path too, but didn't go very far. What sFlow collector are you using?

Best regards,
Alex Bezroutchko

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