[Engine-devel] Question about CloneVMFromSnapshot feature in context of shared disks and direct LUNs-based disks

[Livnat Peer]

On 19/01/12 12:03, Ayal Baron wrote:
> 
> 
> ----- Original Message -----
>> On 01/19/2012 09:19 AM, Livnat Peer wrote:
>>> On 19/01/12 08:38, Yair Zaslavsky wrote:
>>>> Hi all,
>>>> Following the upstream meeting dated Wednesday January 18th, 2012
>>>> -
>>>> I presented the clone VM from snpashot feature and we discussed
>>>> the
>>>> feature behaviour.
>>>>
>>>> Two issues that were raised are the behaviour of the feature in
>>>> context
>>>> of shared disks and direct LUNs-based disks -
>>>> On one hand, if we copy&collapse such images - this may yield to
>>>> data
>>>> corruption (think of a scenario where the source and destination
>>>> VMs use
>>>> the same disk).
>>>> On the other hand - if we decide not to copy&collapse  - the
>>>> target VM
>>>> will have missing VM and its state will not totally reflect the
>>>> logical
>>>> state.
>>>> One of the solution raises is to mark such disks (at the
>>>> destination) as
>>>> unplugged, allowing the administrator the ability to plug them
>>>> (understanding of course the consequences).
>>>>
>>>> I would like to receive inputs on this issue
>>>>
>>>>
>>>> Kind regards,
>>>>
>>>> Yair
>>>
>>> Hi Yair,
>>>
>>> Some clarifications on the above issue.
>>> Currently when taking a snapshot on a VM with shared disks or
>>> direct LUN
>>> disk there are 3 optional behaviors:
>>>
>>> 1. Blocking the snapshot action. (User can not take a snapshot of
>>> the VM
>>> if it has plugged shared or direct LUN disks)
>>>
>>> 2. Taking the snapshot and marking the shared disk and direct LUN
>>> disks
>>> as unplugged (in the VM snapshot configuration) and marking the
>>> snapshot
>>> state as partial.
>>
>> just making sure - this wouldn't change the active running config
>> (when
>> taking a live snapshot)?
> 
> no, only the config of the snapshot.
> 
>> doesn't it mean we could take partial snapshot for any type of disks
>> then (internal ones as well)?

Not in this version, we added the concept of partial snapshot to enable
deleting a disk from a VM with snapshots. We mark all snapshots that
used this disk as partial.

> 
> To do this properly you would need to drive it from the GUI.  Currently the behaviour was defined as implicit (engine would automatically do this according to disk type).
> 
> In any event, even if partial snapshots will not be available in 3.1, the API should get the list of LUNs to snapshot and just raise an error if not all devices were passed.
> Otherwise we'd need a new API for partial snapshots (I'm talking about REST API in case this isn't clear).
> 
>> _______________________________________________
>> Engine-devel mailing list
>> Engine-devel at ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>