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

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. 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.