[one-users] Instance migration based on resources

[Gandalf Corvotempesta]

2013/1/16 Simon Boulet <simon at nostalgeek.com>:
> It's definitively possible to do offline upgrade/downgrade with OpenNebula.
> You need to cancel the VM and submit a new template reusing the image. The
> main problem is the image, you need to make it persistent.


This isn't an issue for us.
We have 2 level of service:
 - one with persistent images
 - one with volatile images

In the first case, we will shutdown the VM, update the template and
then create another VM with the same NIC/HDD configuration. This
should do the trick and automatically migrate the VM on the first
available host.
In the second case, user's will protect their datas on their own, for
example by having multiple instances load balanced with a shared
filesystem between each. In this case, the VM Image is used just for
the OS. we can safely destroy and recreate a new VM with no data loss.
(like amazon does)

Cloud system must be able to fail with no data loss, if user is not
able to protect it's data, it should buy a standard VPS and not a
cloud one with volatile storage.

My only question is to know if, actually, is possible to shutdown an
image (with persistent storage), change the template increasing some
resources and then power it again with no data loss. (and in a very
short time)