[Engine-devel] SharedRawDisk feature detail

[Itamar Heim]

On 02/14/2012 07:44 PM, Livnat Peer wrote:
> On 14/02/12 11:44, Maor wrote:
>> On 02/14/2012 09:17 AM, Livnat Peer wrote:
>>> On 13/02/12 19:44, Maor wrote:
>>>> On 02/12/2012 07:03 PM, Livnat Peer wrote:
>>>>> On 02/02/12 17:15, Maor wrote:
>>>>>> Hello all,
>>>>>>
>>>>>> The shared raw disk feature description can be found under the following
>>>>>> links:
>>>>>>    http://www.ovirt.org/wiki/Features/DetailedSharedRawDisk
>>>>>>    http://www.ovirt.org/wiki/Features/SharedRawDisk
>>>>>>
>>>>>> Please feel free, to share your comments.
>>>>>>
>>>>>> Regards,
>>>>>> Maor
>>>>>> _______________________________________________
>>>>>> Engine-devel mailing list
>>>>>> Engine-devel at ovirt.org
>>>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>>>>
>>>>> Hi Maor,
>>>>>
>>>>> - "when taking a VM snapshot, a snapshot of the shared disk will not be
>>>>> taken."
>>>>> I think it is worth mentioning that the shared disk will be part of the
>>>>> VM snapshot configuration. The disk will appear as unplugged.
>>>> Agreed, I changed it to the following:
>>>> when taking a vm snapshot, a snapshot of the shared disk should not be
>>>> taken, although it will be part of the VM snapshot configuration and the
>>>> disk will appear as unplugged.
>>>>>
>>>>> - Move VM is deprecated in 3.1.
>>>> Right, I removed this anecdote from the wiki.
>>>>>
>>>>> - It seems from the wiki that shared disk is not supported for template
>>>>> but is supported for VM pool.
>>>>> I am not sure how can we do that? iirc we create pool from template.
>>>> What I was thinking about, is that the administrator can take a VM from
>>>> the pool and attach it a shared disk, after the VM was created (for
>>>> testing).
>>>>
>>>> The motivation for adding shared disk was that each entity that can be
>>>> added with a disk can also be added with shared disk.
>>>> Today, Administrator can add a disk to a VM from pool, which might be
>>>> wrong behaviour, so maybe its better not to support it...
>>>>>
>>>>> What is the complexity of supporting shared disk in Templates? off the
>>>>> top of my head it seems like it is more complicated to block shared
>>>>> disks in templates than to support it. What do you think?
>>>> Implementation wize it might be less complex, the problem is the use
>>>> cases it raises,
>>>> some of them which I'm thinking about are:
>>>> * If the disk will be deleted from the DC, should we remove it from the
>>>> template? or leave an indication in the template that there was a shared
>>>> disk there, maybe should not allow to delete the disk in the first
>>>> place, until it is unattached from the template?
>>>
>>> Since template configuration is 'read-only' you can not change a disk to
>>> be plugged or unplugged.
>>> I would say you can not delete a disk that is part of a template
>>> regardless if it is shared or not.
>> So in that case template with shared disk, will block the user from
>> removing the shared disk from the DC.
>> Won't it will make the flow for the user a bit complicated.
>> User who wants to remove the shared disk, will need to remove the VM's
>> which are based on the template and then remove the template it self.
>
> I see the complication of delete, we have similar complications for
> delete regardless of shared disk (deleting disk with snapshots).
>
> Other than delete can you think of other complicated scenarios?

if it makes things more complex, why not postpone this part of the 
feature to a later phase?