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

----- Original Message ----- > > > ----- Original Message ----- > > From: "Livnat Peer" <lpeer(a)redhat.com&gt; > > To: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt;, "Mike Kolesnik" > > <mkolesni(a)redhat.com&gt; > > Cc: engine-devel(a)ovirt.org > > Sent: Thursday, January 19, 2012 9:19:52 AM > > Subject: Re: [Engine-devel] Question about CloneVMFromSnapshot > > feature in context of shared disks and direct > > LUNs-based disks > > > > 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.

> > > > 3. Taking the snapshot of the VM as is, leaving the VM > > configuration > > with plugged disks.

> > > > > > The issue with including these disks in the snapshot is that they > > are > > not really being snapshotted, they are not capturing the point in > > time > > we are trying to achieve in the snapshot. > > > > Enabling the snapshot action in such a state is a bit misleading > > to > > the > > user. > > > > If we do allow taking the snapshot we should mark the snapshot as > > partial to indicate that the snapshot did not capture the point > > in > > time > > as the user intended.

> > > > I have no preference with regards to the second and third > > approach, > > the > > second approach is a bit more safe, we basically force the user > > to > > plug > > the disks and be sure that he knows what he is doing and the > > third > > approach is less safe and less annoying to the user (he took the > > snapshot, cloned it and wants to start the VM - don't require > > extra > > actions) > > > > Kolesnik - please note when starting VM in a preview mode we > > should > > mount the disks in read-only mode (if supported).

I don't understand this, can you please elaborate why and in which case? The disk is plugged/unplugged? What happens when you commit? It becomes r/w?

> > > > > > Livnat > > > > > > > > +1 for option 3 > +1 for option 3 as well (also good with option 1, but I think this will hinder usability). Regards, Mike _______________________________________________ Engine-devel mailing list Engine-devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel