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Re: [Xen-users] domU loses network after a while

To: Nathan Friess <nathan@xxxxxxxxx>
Subject: Re: [Xen-users] domU loses network after a while
From: Rudi Ahlers <Rudi@xxxxxxxxxxx>
Date: Mon, 15 Nov 2010 09:33:17 +0200
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On Mon, Nov 15, 2010 at 8:00 AM, Nathan Friess <nathan@xxxxxxxxx> wrote:
> Hi,
> I have a host running Debian Squeeze with Xen 4.0.1 installed from the
> Debian repository.  My host is working fine running 10 domUs, except that
> after some number of days one or more domUs lose their network interface.
>  In dom0 and domU I'm running kernel 2.6.32-5-xen-amd64 (PV kernel in Debian
> repo), and interfaces are in a bridged config.
> When the network dies eth0 in domU is up as well as vif in dom0, but it
> seems like no unicast packets make it to/from the domU and dom0.  I can run
> wireshark on the dom0 on vif and see packets attempt to be sent to the domU,
> but I don't have wireshark installed in the domU to verify what is actually
> received.
> The only thing that I can see coming from domU in wireshark is ARP
> broadcasts and replies are attempted to be sent, but domU never receives
> them (arp command shows 'incomplete').  The only other odd thing I see is
> that the load average is 17 or 18 in each affected domU, while normal domUs
> are 0 load average.  Nothing helpful in dmesg.
> At first I had one domU do this after maybe 30 days uptime.  Then another
> did it about 2 weeks later.  Now three of them are doing the same thing 8
> days later and all three started at the same time (plus or minus a few
> minutes?).  The only fix seems to be to restart the domU. ifdown/up doesn't
> seem to help.
> Is there any way to figure out why domU never receives unicast packets?  Is
> there any other useful info that I can collect to help track down the cause?
> Thanks,
> Nathan
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You need to try and figure out why the load is so often. I have seen
many times that when the load goes high, network activity drops. Maybe
the server is overloaded? If you have too high IO use, it will start
consuming RAM & CPU above what is needed and cause high load.
Kind Regards
Rudi Ahlers

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