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Re: [Xen-users] XCP ethernet jumbo frames????

To: Rob Hoes <Rob.Hoes@xxxxxxxxxx>
Subject: Re: [Xen-users] XCP ethernet jumbo frames????
From: Gémes Géza <geza@xxxxxxxxxxx>
Date: Tue, 21 Sep 2010 17:54:00 +0200
Cc: James Harper <james.harper@xxxxxxxxxxxxxxxx>, "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>
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2010-09-21 11:42 keltezéssel, Rob Hoes írta:
> Jumbo frame support was still in development when XCP 0.5 was released. 
> Though it may work, you probably should not rely on what the PIF.MTU and 
> VIF.MTU fields tell you (in the most recent XCP snapshot this should have 
> been fixed). You should still be able to use ifconfig to find the MTU.
> Important is that you unplug and plug all VIFs and PIFs that are connected to 
> a network after changing the network's MTU, otherwise nothing happens. Could 
> you try this?
> Cheers,
> Rob

I'm absolutely sure that all the interfaces have been reinitialized
because I've restarted the Dom0 after setting the MTU at the network.
>> -----Original Message-----
>> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
>> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Gémes Géza
>> Sent: 21 September 2010 06:00
>> To: James Harper; xen-users@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-users] XCP ethernet jumbo frames????
>> 2010-09-21 00:27 keltezéssel, James Harper írta:
>>>> Hi,
>>>> I have an XCP 0.5 box running a few DomUs some of the DomU's data is
>>>> stored at (clustered lvm volumes on) a Coraid etherdrive box which
>> is
>>>> connected via an Ethernet cable to a dedicated card of the XCP box,
>> for
>>>> which in the network config I' ve specified: MTU=9344: xe
>>>> network-param-list uuid=.... gives:
>>>> MTU ( RW): 9344
>>>> on the DomUs if I leave the MTU at 1500 (default settings)
>> everything
>>>> works (slowly, but works). If I increase the MTU the aoe device
>> appear
>>>> as expected, but the data on it becomes inaccessible, even just
>> trying
>>>> to activate the lvm volume groups gives a bunch of IO errors at
>> sector
>>>> 0, and so on.
>>>> Please tell me what I'm doing wrong. Are jumbo frames expected et
>> all to
>>>> work?
>>> Does your network adapter really support jumbo frames?
>>> Is the network adapter on a bridge? (I'm unsure if Dom0 does AoE or
>> if the DomU's do)
>>> Are all the bridge interfaces set to 9344 MTU?
>>> Could tcp offload settings break any of this? (unlikely - AOE is not
>> TCP)
>>> tcpdump might tell you what's going on.
>>> James
>> The network adapter seems to be ok.
>> I've tried to do aoe at the DomU's.
>> I've set the network bridge's MTU at the bridge which is connected with
>> the Coraid box.
>> After some tcpdumping I've checked what the good old ifconfig would say
>> about my interfaces. Surprisingly while xe network... reports MTU=9344
>> ifconfig says it is at 1500 (the vifs attached to the bridge have 9344
>> ), while xe pif... reports all interfaces to have MTU=1500 (I have an
>> other interface set at MTU=4200, which shows itself even with ifconfig
>> as having MTU=4200). I start to get really confused :-(
>> Cheers
>> Geza
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