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

[Ayal Baron]

----- Original Message -----
> On 01/22/2012 09:26 AM, Livnat Peer wrote:
> > On 20/01/12 17:21, Itamar Heim wrote:
> >> On 01/20/2012 12:01 PM, Livnat Peer wrote:
> >>> On 20/01/12 09:35, Ayal Baron wrote:
> >>>>
> >>>>
> >>>> ----- Original Message -----
> >>>>> Top Posting:
> >>>>>
> >>>>>  From user POV I think that option 2 is the only one that make
> >>>>>  sense.
> >>>>> We try to do as much as we can,
> >>>>> and on each "problematic" case, we make him aware and let him
> >>>>> decide.
> >>>>>
> >>>>
> >>>> Yep, +1.
> >>>>
> >>>
> >>> Trying to get to a conclusion here,
> >>> 3 different people said on this thread that they think that from
> >>> the
> >>> user perspective leaving the shared devices plugged is what they
> >>> think
> >>> is the best behavior to the user. (Omer, Kolesnik, Yair)
> >>>
> >>> On the other hand we have 2 people who think that protecting the
> >>> user is
> >>> more important than leaving the VM configuration as it was in the
> >>> original VM (Miki, Ayal).
> >>>
> >>> Ayal/Miki can you please specify what are we protecting the user
> >>> from?
> >>>
> >>>
> >>> I think that because we are not snapshotting the shared disk and
> >>> the
> >>> direct LUN they should not be part of the VM configuration (in
> >>> the
> >>> snapshot) at all. we can not promise the user that the disk will
> >>> be
> >>> there and if it is there we can not guarantee it is in the same
> >>> state as
> >>> it was when we took the snapshot.
> >>>
> >>>
> >>> Another issue,
> >>>
> >>> I can not see a reason to limit this feature to creating a VM
> >>> from
> >>> snapshot and not a template? Almost no extra work is needed for
> >>> supporting templates as well.
> >>
> >> I assume you meant, creating a VM from another VM (if it is down)?
> >> It should be supported.
> > 
> > Actually I meant creating a Template from Snapshot.
> Livnat - I think that in case of creating a template from snapshot we
> should should have new API/Command, that will probably have lots in
> common with Create VM from snapshot.

Why?

> 
> > 
> > What you suggested is creating a VM from VM.
> > Although I see how the two are connected, I think they should be
> > modeled
> > as two different API calls.
> > There is a difference in the flow, behavior, locks and parameters
> > between the two.
> > 
> > Behavior:
> > - Original VM has to be down for creating a VM from VM, not the
> > case for
> > creating a VM from snapshot.
> > 
> > parameters:
> > - Creating VM from snapshot should support getting a snapshot-ID,
> > Creating VM from VM get a VM id
> > 
> > Locks:
> > - When creating a VM from VM, we need to lock the original VM as a
> > whole, we can not edit the VM, take snapshot or any other VM level
> > action while such operation is active.
> > While for creating the VM from snapshot we can take more
> > fine-grained
> > locks (only image related locks).
> > 
> > Implementation:
> > Well it is simply another implementation.
> +1 on Livnat's explanation - I do see a (design/implementation wise)
> an
> option for some code reuse, but IMHO - this should be a new command
> with
> new API modelling
> > 
> > 
> > Livnat
> > 
> > _______________________________________________
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> > Engine-devel at ovirt.org
> > http://lists.ovirt.org/mailman/listinfo/engine-devel
> 
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