On a general note a user would expect that the delay during migration will be 
higher than the delay while resizing. Also, in this case it appears that the 
resizing functionality performs migration rather scaling up or down the VM. Can 
I get to know the resizing options using which the instance can be retained on 
the same compute node? Can I also get to know whether the scheduler checks for 
the new hardware requirements on the original compute node before it migrates 
to the new compute node?
From: [email protected] 
[mailto:[email protected]] On Behalf 
Of Narayanan, Krishnaprasad
Sent: Montag, 10. Dezember 2012 22:54
To: Vishvananda Ishaya
Cc: [email protected]
Subject: Re: [Openstack] Server resize API in OpenStack ESSEX

As you had mentioned I went through the logs and I could see an error message 
with the "Host Key Verification Failed with exit code 255 on Command: ssh IP 
address mkdir -p /var/lib/nova/instances/instance-000000155". If I get it 
correctly, this means that the key on the compute nodes that was cached earlier 
has been changed. Can I get to know is this correct and how to get rid of this 
problem?
From: Vishvananda Ishaya [mailto:[email protected]]
Sent: Montag, 10. Dezember 2012 20:23
To: Narayanan, Krishnaprasad
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [Openstack] Server resize API in OpenStack ESSEX

The code scps the backing file for the instance to the new node via something 
along the lines of:
scp /var/lib/nova/instances/instance-xxx/disk 
<hostname>:/var/lib/nova/instances/instance-xxx/disk
So the hostname has to properly resolve to the ip of the target machine. You 
should see messages in the compute log about it trying to do this. The error 
message there might give you a better idea of what failed.

Yes resize will go through the scheduler and usually find a new compute node. 
The conf option does not force it to use the same host, so it is mostly just 
there for testing.

Vish

On Dec 10, 2012, at 11:12 AM, "Narayanan, Krishnaprasad" 
<[email protected]<mailto:[email protected]>> wrote:

Hi Vish,


Thanks for the quick reply. I have passwordless ssh between the compute hosts 
but could you explain me the first option. When I resize, will the instance 
redeploy on a different compute node?

Do I need to specify this flag allow_resize_to_same_host=true in nova.conf of 
the compute node?



Regards,

Krishnaprasad
From: Vishvananda Ishaya [mailto:[email protected]<http://gmail.com>]
Sent: Montag, 10. Dezember 2012 20:03
To: Narayanan, Krishnaprasad
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [Openstack] Server resize API in OpenStack ESSEX

2 requirements:

1) hostname for compute hosts resolve properly
2) passwordless ssh works between compute hosts.

Vish

On Dec 10, 2012, at 10:37 AM, "Narayanan, Krishnaprasad" 
<[email protected]<mailto:[email protected]>> wrote:


Hallo All,

I am trying to use the Nova API (POST call) for changing the flavor information 
(to resize) from m1.tiny to m1.medium. Even though the API is successful (202 
Status code), on the Horizon GUI I could see that the Status is Error and the 
task state is Resize Prep. I am passing the Auth Token along with the Body 
information in the form of json as inputs to the API. I have referred this 
URI<http://docs.openstack.org/api/openstack-compute/programmer/content/resizing-servers.html>
 for passing the body information.

I am using OpenStack ESSEX and can I get to know is there any configurations 
that I need to do in order to get this working?

Thanks
Krishnaprasad
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