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Re: [libvirt] VN-Link vNIC memory state copying on VM Migration



Chris

Thanks

Jagath


On Wed, Apr 18, 2012 at 3:40 AM, Christian Benvenuti (benve)
<benve cisco com> wrote:
>> -----Original Message-----
>> From: Jagath Weerasinghe [mailto:jagfoss gmail com]
>> Sent: Tuesday, April 17, 2012 8:19 AM
>> To: Christian Benvenuti (benve)
>> Cc: libvir-list redhat com
>> Subject: Re: [libvirt] VN-Link vNIC memory state copying on VM Migration
>>
>> Chris
>>
>> >> OK. In phase 3, the RAM used by VM in source host is copied to the
>> >> destination. Then what about the memory state of vNIC's in the M81KR VIC.
>> >> Isn't there any memory for traffic passing through vNICs and also for
>> >> vNIC statistics?  What I am talking about is copying of this memory to the
>> >> destination vNIC.
>> >
>> > No, that data (statistics, etc) are not copied to the dst host/vnic.
>> > However, you can find those statistics/counters on the switch (which are
>> > preserved across live migrations).
>>
>> OK. I think this operation is the same for both IEEE802.1qbh (VN-Link)
>> and IEEE802.1qbg. Is that correct?
>
> I assume so.
>
>> One more thing. Could you please tell me where the port profile
>> association/dissociation messages of libvirt are converted to
>> VIC protocol messages. Is this done by CNA it self?
>
> Yes, the NIC firmware takes care of it.
>
> /Chris
>
>> >> > (*) See the migration parameter 'migrate-setmaxdowntime'
>> >> >
>> >> > In phase 4 libvirt applies the port profile to the interfaces
>> >> > that need it and starts the VM (which had been created and put in
>> >> > pause state in phase 2).
>> >> > There is therefore a small period during which both VMs (the one
>> >> > on the source host and the one on the destination host) are in pause
>> >> > state (see dotted lines above).
>> >> > Phase 4 will start the VM on the dst host,
>> >> > Phase 5 will kill the (paused) VM on the src host.
>> >> >
>> >> > The amount of time during which both VMs are in pause state depends on
>> >> > a number of factors, including:
>> >> > - maxdowntime:  the smaller you configure this value and
>> >> >                - the longer will take the migration to complete, but
>> >> >                - the smaller the pause duration will be
>> >> > - bandwidth available on the interface/s used to carry the migration
>> >> >  traffic, and amount of RAM assigned to the VM (since you need to
>> >> >  copy it)
>> >> > - time taken to complete the port profile associations on the dst host
>> >> >  (which depends on how loaded the switches are)
>> >> > - ...
>> >> >
>> >> >
>> >> > Hope this clarifies a bit.
>> >> > /Chris
>> >> >
>> >> >> If this memory state (or traffic) is not copied and moved to the
>> >> >> destination vNIC how the smooth communication, which is
>> >> >> guaranteed on VM migration, is achieved?
>> >> >>
>> >> >> Thanks
>> >> >> Jagath
>> >> >>
>> >> >> >
>> >> >> > If you refer to port profile info, then there is no copying involved:
>> >> >> >  the source host disassociates the vnic port profile and
>> >> >> >  the destination host re-associates the port profile on the new vnic.
>> >> >> >
>> >> >> > /Chris
>> >> >> >
>> >> >> >> -----Original Message-----
>> >> >> >> From: libvir-list-bounces redhat com
>> >> >> > [mailto:libvir-list-bounces redhat com] On Behalf Of Jagath
>> >> >> >> Weerasinghe
>> >> >> >> Sent: Friday, April 13, 2012 9:16 AM
>> >> >> >> To: libvir-list redhat com
>> >> >> >> Subject: [libvirt] VN-Link vNIC memory state copying on VM Migration
>> >> >> >>
>> >> >> >> Hi All,
>> >> >> >>
>> >> >> >> I am new to libvirt. And want to know how the VM migration
>> >> >> >> occurs in VN-Link (IEEE802.1Qbh). As far as I know,
>> >> >> >> the memory state of vNICs in M81KR VIC has to be copied
>> >> >> >> and moved to the destination vNIC on VM migration.
>> >> >> >> Is that correct? If so, could you please tell me how this
>> >> >> >> has been implemented in libvirt?
>> >> >> >>
>> >> >> >> Thanks
>> >> >> >> Jagath
>> >> >> >>
>> >> >> >> --
>> >> >> >> libvir-list mailing list
>> >> >> >> libvir-list redhat com
>> >> >> >> https://www.redhat.com/mailman/listinfo/libvir-list
>> >> >>
>> >> >> --
>> >> >> libvir-list mailing list
>> >> >> libvir-list redhat com
>> >> >> https://www.redhat.com/mailman/listinfo/libvir-list


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