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

[Jagath Weerasinghe]

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?

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?

Thanks
Jagath



>
> Thanks
> /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 at redhat.com
>> >> > [mailto:libvir-list-bounces at redhat.com] On Behalf Of Jagath
>> >> >> Weerasinghe
>> >> >> Sent: Friday, April 13, 2012 9:16 AM
>> >> >> To: libvir-list at 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
>> >> >>
>> >> >> --
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>> >>
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