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VEM Interaction

pfazzone
Level 1
Level 1

Posting this question on behalf of one of our customers:

When creating a profile, is that profile really (!) on all VEMs?

PF> No, it exists on the VSM and the rules contained in the Port Profile are pushed down to the VEM as a new VM is created in vCenter requesting access to that Port Profile.

Or will it be pushed to the VEM only when VMotion occours or a VM will be connetcet to it?

PF> Correct, the rules of the Port Profile get pushed down to the Virtual Ethernet interface the VM is connected to when the VM is created and follows that VM during vMotion events.

Background: I would like to knoe whether there is any interaction between VEM and VSM in case of VMotion.
I have read that yes there is interaction. But a little test confused me.
I created a port-profile and shut down the VSM. Anyway it was possible to connect a VM to that profile also
VMotion was no problem.

PF> Did you specifiy this Port Profile used in this test as a system profile? Or just a regular profile?  If it was a system profile, this would work.  If it was a regular port profile, this should fail.

Thanks,

pf

6 Replies 6

backhausenm
Level 1
Level 1

Hello Paul,

thanks for your answer. In my little test I created a regular profile, shut down the VSM but could vmotion anyway to a host

where the new profile was never used before. How can that be?

THanks and Regards,

MAtthias Backhausen

Fujitsu

Hello Matthias,

The vMotion won't be prevented, but I bet that the VM that you moved (was it actually sending traffic?) was no longer able to connect to the ouside world.  Can you confirm?

Update 1:  If the VM is using the same VLAN as one of the system VLANs, it will still have connectivity even after a vMotion with the VSM down.

Thanks,

pf

Hi,

There is indeed an interaction between the VSM and the VEM in the case of a VMotion process. This can be verified the way that Paul described it:

During a VMotion the virtual port is moved from one VEM to another. Thus not all ports/VLANs exist on all VEMs at all time.

Thus the result is, that if you kill/shutdwon the VSM, the VMotion will still suceed (no error message), but the virtual port will not move along as the entity which is in charge of doing so is dead. Thus after the VMotion the VM looses connectivity. Also after you bring up the VSM again, it will sync the information about the port-profiles/port-groups with the vCenter. As a result, the virtual ports will be re-configured and loose connectivity for a short moment.

All this applies if you do not configure the corresponding VLAN as a system VLAN.

In case the VLAN is configured as a system VLAN, the port is not touched by the VSM but remains up and operational from the moment that the VEM is brought up. This means that a VMotion or VSM restart will not do anything to the connectivity.

Therefore the recommendation for using system VLANs is to specify the following traffic classes/ports/interfaces to leverage system VLANs:

- Service Console

- VMKernel VMotion

- VMKernel Fault Tolerance

- IP based storage (iSCSI/NFS)

Hope that helps.

Chris

Hello Paul,

confirmed!

Thanks and Regards,

Matthias

Hi Mathias,

I also would like to add the following to this discussion.

If the VSM is deployed in a Active/Standby HA (CIsco HA) mode (which is our recommended deployment model), even if the primary VSM fails for any reason, the VMotion events will be un-affected because the standby VSM will take over and the ports on the VMotioned VM will be brought up on the destination host.

- Saravan

stevediaz
Level 1
Level 1

Hello

The Port Profile exists on the VSM and its rules are pushed to the VEM when a VM is created and during VMotion events. If the Port Profile is a system profile, it can work even if the VSM is offline, but a regular profile should fail if the VSM is shut down.

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