[one-users] templates and images explanation needed

[Bart]

Hi,

I'm running against this same issue as described here.

Regardless of how I try to look at it, non-persistent  (and thus, volatile
images) are kinda annoying.

I understand how to create a template, install an OS using that template
(CDROM and persistent OS images linked) and then after installation marking
the OS image as non persistent which then can be used to deploy multiple
VM's with that image as "base".

But what I would expect (in experience with other virtualisation
technologies) is the creation of a clone image in the *Image datastore*,
which would be linked to the new VM. But instead I see that these VM's use
the non persistent image, which is physically stored in the *System
datastore* and at that point it's still a volatile image. Also, when
shutting down that VM it simple deletes it all together (same as
any volatile image, I really don't see the point of it).

So basically, de deployment works, but what I want is the deployment of
"persistent" images (in the image datastore) which are based on a "non
persistent" base image. Is this at all possible?

So in any way, my questions are pretty much the same as Pawel.

Based on this topic I don't see any answers, so could someone please help
us understand how this is all supposed to work and what the basic idea is
behind it all?

Thanks in advance!!!



2014-07-22 17:05 GMT+02:00 <pawel.orzechowski at budikom.net>:

>  After reading the ON docs and explanation from panoramisk I understand
> the behaviour of persistent vs non-persistent image. But I do not get idea
> behind this. It seems to be opposite to ON simplicity.
>
> We had a following situation:
>
>    - the machine was running with non-persistent image disk,
>    - I created hot snapshot, then I create next but deferred snapshot
>    - Then I thought I do not need deferred snapshot so I deleted the image
>    - Now when I wanted to create next snapshot I could not because I got
>    error "the disk 0 will be saved"
>    - In the VM view of this particular VM at storage tab there was my
>    original non-persistent image but with ID of the deleted image and
>    information that it is persisent
>    - Now the only way to clear this situation was to shutdown VM which
>    caused that it was deleted
>    - the last state of data was in the image created from hot snapshot
>
> Based on this and also our current experience with VMware or XenServer
> environments I do not really get this image/template idea in OpenNebula, so
> please again can someone clarify:
> 1. What is the "business" purpose of a non-persistent image?  What are use
> cases here? (I suppose one is some goldencopy)
> 2. Can the deployment of virtual machine with persistent image from
> non-persistent image be simpler? Now having non-persistent image (eg. from
> ON marketplace) one has to clone it than change it to persistent, then
> create template with this image and then instantiate virtual machine from
> this. Now when I want to create another, bunch of virtual machines with
> persistent images I have to create bunch of copies of non-persistent image
> and create image with each of them and then from each instantiate VM - this
> is not simple but it should be.
> 3. In the case of this persistent images what is the case for template
> here, if I can not use template twice - once I create VM from template with
> persistent image I can not used it again because image is persistent and
> data is being written to him - the solution here is that while creating VM
> from "persistent" template it should automatically copy image to a new one
> for use in VM so the next VM could be created.
> 4. If I have VM running with non-persistent image there should be a way to
> switch VM to persistent image without loosing data.
>
> Thanks
>
> Pawel
> --
>
> Paweł Orzechowskipawel.orzechowski at budikom.net*budikom.net <http://budikom.net>*
>
>
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>


-- 
Bart G.
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