[Engine-devel] Clone VM from snapshot feature

[Yair Zaslavsky]

On 02/14/2012 11:03 AM, Yaniv Kaul wrote:
> On 02/14/2012 10:53 AM, Yair Zaslavsky wrote:
>> On 02/14/2012 10:35 AM, Yair Zaslavsky wrote:
>>> On 02/14/2012 10:29 AM, Yaniv Kaul wrote:
>>>> On 02/14/2012 10:06 AM, Yair Zaslavsky wrote:
>>>>> Hi all,
>>>>> I modified the Wiki pages of this feature:
>>>>>
>>>>> http://www.ovirt.org/wiki/Features/CloneVmFromSnapshot
>>>>>
>>>>> http://www.ovirt.org/wiki/Features/DetailedCloneVmFromSnapshot
>>>> - Missing error handling. I hope all will goes well, of course.
>> Will be added. Not sure though what can we do in case for example you
>> fail to copy image N out of M , besides of course
> 
> Since it's not clear that if you merge the snapshots regardless of the
> base image (if it's RAW), or you merge them all to one big image, I'm
> not sure if there are two processes here or not - I assume there are:
> copy and merge. Each can fail independently, and rollback is probably
> required?
> 
>>>> - Will you be copying the disks in parallel, or serially?
>> CopyImage is an asycnrhonous verb that will be monitored by the
>> AsyncTaskManager at Engine core.
> 
> Which means that if there are N disks you copy them in parallel or one
> by one? May make sense to do it depending on the storage domain - if
> it's the same for all or not, etc. An optimization, I guess.
This engine core code that is required to launch VDS command + create a
task for monitoring it takes less time than completion of the monitoring
itself - so the part of lauch VDS command + create task for monitoring
is serial, but the monitoring itself is performed periodically,
according to the behavior of AsyncTaskManager.
Engine-core is indifferent to whether the copies are performed
concurrently or not in VDSM.



> 
>>
>>>> - Too bad the disks have to be copied by the SPM. Not sure why, really.
>>> Typo, will be fixed.
>>>> Same for the merge, which is not really mentioned where/how it's going
>>>> to take place (VDSM-wise).
>> The copy operation will perform collapse on destination.
>> Maybe I do not understand your question here-  please elaborate.
> 
> Will the merge of the snapshots be done by SPM or HSM?
> 
>>
>>>> - If the 'Disk1' , 'Disk2' are RAW, would be nice to have an option NOT
>>>> to copy them. Especially as you have a snapshot on top of them.
>> Please elaborate on that.
> 
> If you are going to merge snapshots into the base, not sure it needs to
> be copied first - I wonder if there's an option to collapse to a new
> destination. QEMU feature, I guess.
> Y.
> 
>>>> Y.
>>>>
>>>>> Comments are more than welcome
>>>>>
>>>>> Kind regards,
>>>>> Yair
>>>>>
>>>>>
>>>>>
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