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Lab 3.2 - Problem and Doubt



Hi all,

I´m running the Lab 3.2 and I have the following issues and doubs:

1- The compute-node was created correctly. it's possible to see in Openstack (admin) the expected two hosts;

2- When I tried to create de DevOS3, I recevied an Error msg [Unkown] requesting to try latter.  Why? Is there any wrong configuration in the previous steps? OBS: I tried to run these steps twice and in different days, without sucess.

3- Even considering this Error status in DevOS3 instance, it's possible to see clearly that this instance was launched considering to use the resources in the new host created - compute-node. My doubts are::

a) Why this host was selected to support this instance deployment?

b) Some kind of data and/or configuration pointed this deployment to the new host as the target for this deployment? Which parameters?

c) How could I change the deployment of DevOS3 to the other host (devstack-cc)? Trying to "exercise" some possible scenario involving instance launching x hosts with problems....  

Thanks in advance.







  • serewicz
    serewicz Posts: 1,000
    edited July 2016


    The choice for instance deployment rests with nova-scheduler. If all compute hosts are of equal memory and cpu capability the choice is round robin. If one has more resources the default behaviour is to deploy instances on that node until it runs out of resources and then decide the next node to use.

    One of the ideas behind OpenStack is to deploy instances without having to do much more than click a button. As a result if you want to override the selection there is more typing required. The use of an availability-zone parameter will allow you to choose which compute-hosts an instance will be deployed upon. This would need to be configured prior to deployment or moved via evacuation after deployment. 

    If you want to avoid a host you can disable the service, deploy an instance and enable the service once the issue has been resolved.



  • Robson Esteves

    serewicz, thanks!

    Very clear.





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