PowerVC

As an admin user, bringing back migrated virtual machines becomes your overhead. Agreed?!

Identifying virtual machines that were moved to a viable host and manually bringing them back becomes an overhead for an admin user in the following scenarios:

• During host maintenance


• When a host that has ARR enabled goes down

No worries! PowerVC has the solution for you.
With PowerVC 1.4.4, admin users can use the ‘Recall virtual machine’ feature to automatically bring virtual machines back to the original host. Users can enable the recall VM capability on a host. They can set this capability to 'Yes' / 'No' on the host details page. If this capability is set to ‘Yes’, any VMs that were moved from this host during Maintenance Mode or ARR will be automatically recalled/migrated back to this host once the host is back to operating state.

Recall VM through user interface

To recall a virtual machine to a host, perform the following steps:

1. Go to the host details page and choose to edit details.


2. Click to edit “Recall enabled:” feature.
   


3. Select the check box and click OK. This enables the recall virtual machine feature for specific host.

When this host is moved to maintenance mode or goes down (and has ARR enabled), PowerVC moves the virtual machines to a viable host. Later when this host comes back to operating state, after 5 minutes PowerVC will automatically bring back the virtual machines to this host.

Example scenario:
Virtual machines vm1, vm2… and vmN on source host A moved to a destination host B. In a case where host B also goes down (and has ARR enabled), PowerVC moves virtual machines to another viable host C. When the source host A comes back to operating state, PowerVC brings back vm1, vm2… and vmN to source host A.
During this scenario, even if host B comes back to operating state (and has Recall feature enabled), vm1, vm2…vmN will still move to host A as PowerVC considers only the original host.

What if recall fails?
Recalling virtual machine might fail in a few scenarios like resource constraints on the host. You can fix the issues and manually trigger recall virtual machine feature.

When recall fails, the ‘Recall virtual machine’ button is enabled as shown in the below picture.



Click Recall virtual machine to recall virtual machines manually.

What if I want to recall only a few virtual machines from the new host?
You can pin those virtual machines by using “Pin VM” feature on the new host.

What if I want to avoid movement of a few virtual machines during maintenance mode and ARR from the specific host?
You can hard pin the virtual machines on the specific host.

For more details on pinning virtual machines on a host, see "Pin Virtual Machines".

Recall VM through REST API

Given below is an example that explains the procedure to recall virtual machines through REST API.

Method: PUT
URI: /v2.1/{tenant_id}/os-hosts/{host_name}/recall-vm
Request parameters:
Request body doesn't not take any parameter and it will be empty.
{}
Response codes:
   Normal response code: OK (202)
   Error response code: Forbidden (403), Not found(404), to many requests(429), pre condition failed (412)

Response body:
    Since recall-vm is asynchronous call there will not be any response body as well.             
curl eg:
curl  -X PUT URI -H "Accept: application/json" -H "Content-Type: application/json" -d '{}' -H "X-Auth-Token: 

If you have any questions about this topic, please comment below. Watch this space for more information about troubleshooting your environment. In the meantime, don't forget to follow us on LinkedIn, Facebook, and Twitter.

Blog Authors
Madhavi Yenugu
Vijayendra Radhakrishna
#Compute