[Engine-devel] the future of template cloning

[Omer Frenkel]

----- Original Message -----
> From: "Itamar Heim" <iheim at redhat.com>
> To: "Jon Choate" <jchoate at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Monday, January 16, 2012 7:26:24 PM
> Subject: Re: [Engine-devel] the future of template cloning
> 
> On 01/16/2012 06:16 PM, Jon Choate wrote:
> > On 01/16/2012 10:58 AM, Itamar Heim wrote:
> >> On 01/16/2012 05:46 PM, Jon Choate wrote:
> >>> On 01/16/2012 09:46 AM, Livnat Peer wrote:
> >>>> On 12/01/12 22:45, Ayal Baron wrote:
> >>>>>
> >>>>> ----- Original Message -----
> >>>>>> We are going to be able to store the disks for a template on
> >>>>>> different storage domains due to the multiple storage domain
> >>>>>> feature. Cloning a template will still be possible, but will
> >>>>>> it
> >>>>>> provide any value? Thoughts?
> >>>>> I see no relation between the two options.
> >>>>>
> >>>>> Scenario 1: I can create a VM with a single disk and create a
> >>>>> template from it.
> >>>>> I would still want to be able to clone the template in order to
> >>>>> provision VMs from it on different domains.
> >>>>>
> >>>>> Scenario 2: same thing with multiple disks on same domain.
> >>>>>
> >>>>> Scenario 3: I have a template with 2 disks on 2 different
> >>>>> domains
> >>>>> (domain A and domain B) and I want to have another copy of the
> >>>>> template on domain C and domain D
> >>>>>
> >>>> Hi Jon,
> >>>>
> >>>> After talking to Michael Pasternak it seems that we did not
> >>>> implemented
> >>>> copyTemplate in the REST API, it seems to be a gap that we have.
> >>>>
> >>>> This gap is playing in our favor, we can remove the copyTemplate
> >>>> verb
> >>>> and introduce copyDisk verb.
> >>>>
> >>>> The template disks can be copied to another SD.
> >>>> When creating a VM from template the user can choose per disk
> >>>> the
> >>>> destination SD (only SD with the disks are eligible candidates).
> >>> wait, when creating a VM from a template, the user won't get a
> >>> choice
> >>> will they? Won't the VM disks have to go on the same storage
> >>> domain as
> >>> the template disks they were created from?
> >>
> >> yes, but the template disks can be copied to multiple storage
> >> domains,
> >> so the user can choose for the VM/disk which storage domain to
> >> create
> >> them from (per storage domains that have copies of that disk)
> > OH! I totally misunderstood. So what you are saying is that a
> > template
> > can have N number of copies of the same disk each on a different
> > storage
> > domain. I had thought that if you wanted that type of situation you
> > would have multiple copies of the template itself too.

yes, one copy of disk per domain though.

> >
> > Just to be clear, does this mean that the plan is to phase out the
> > current clone template command and instead implementing a clone
> > disk
> > command so that a template can duplicate its disks individually?
> 
> pretty much, yes.
> though i'd imagine 'clone template' would still be useful to have for
> the user. not sure if it implies core should expose it as well to
> allow
> easier usage at UI level for such a task.

we can leave it untouched - means copyTemplate get 1 destination domain, and copies all disks to it,
but i think it will be unusable (and problematic - what if one of the disks already exists on the destination?), 
what the user really wants is to specify which disks to copy
and destination per disk, and i don't see a reason to create a backend command to do it

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