[Engine-devel] the future of template cloning

[Itamar Heim]

On 01/17/2012 10:32 AM, Omer Frenkel wrote:
>
>
> ----- 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?),

then don't copy it, it is already there

> 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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