-----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
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