[Users] Templates and originating VM relationship

[René Koch (ovido)]

Hi Gianluca,

@oVirt-team: please correct me if I misunderstood something on the
template-concept...

Unlike Vmware (which converts a vm into a template) RHEV/oVirt is
copying the vm into a template.

So you can remove or edit your original vm without having an impact on
your template.

More important is the template provisioning method when creating vms
from your template. If you choose Thin, only changes between your
template and your vm are written to your vms disk file, where clone
creates a clone of your template's disk. Template thin provisioning
saves disk space, but you can't delete the template as long as you don't
delete all vms linked to this template.

The name of your disk is just a name (and it seems that it doesn't have
to be unique) - important is the ID, which is used by oVirt internally.


Regards,
René




On Tue, 2013-03-26 at 15:11 +0100, Gianluca Cecchi wrote:
> Hello,
> oVirt 3.2.1 on Fedora 18.
> I customize a CentOS 6.4 VM and when I comfortable I select "make template".
> I don't take any snapshot for the VM before this.
> 
> I thought that VM would have been disappeared, transforming itself
> into a template, instead at the end I have both the template and the
> originating VM.
> Apparently with the same name for the disk and the same storage domain....
> 
> What is exactly the relationship between them?
> Can I safely remove the originating VM?
> 
> I already tested making template and then deleting it and then being
> able to power on again VM and make a new template from the originating
> VM.
> 
> The rhevm 3.1 admin manual is not so clear about this: it contains a
> note regarding
> "
> Take a snapshot of the virtual machine at this stage if you wish to
> use the virtual machine
> (as a virtual machine) after using it to create a template.
> "
> 
> But if behavior of oVirt 3.2.1 has to be the same with it, this
> doesn't explain itself based on my experience....
> 
> Thanks in advance for any information
> 
> Gianluca
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