[Engine-devel] VM disks

[Daniel Erez]

----- Original Message -----
> From: "Livnat Peer" <lpeer at redhat.com>
> To: "Itamar Heim" <iheim at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Sunday, February 19, 2012 1:23:56 PM
> Subject: Re: [Engine-devel] VM disks
> 
> On 19/02/12 12:35, Itamar Heim wrote:
> > On 02/18/2012 07:07 PM, Livnat Peer wrote:
> >> Hi,
> >>
> >> These days we are working on various features around VM disks, in
> >> the
> >> different threads it was decided that we'll have the ability to
> >> attach a
> >> disk to a VM but it will be added as inactive, then the user can
> >> activate it for it to be accessible from within the guest.
> >>
> >> Flow of adding a new disk would be:
> >> - creating the disk
> >> - attaching the disk to the VM
> >> - activating it
> >>
> >> Flow of adding a shared disk (or any other existing disk):
> >> - attach the disk
> >> - activate it
> >>
> >> It seems to me a lot like adding a storage domain and I remember a
> >> lot
> >> of rejections on the storage domain flow (mostly about it being
> >> too
> >> cumbersome).
> > 
> > true, you'll be asked to provide an option for the initial state in
> > that
> > case.
> > 
> >> After discussing the issue with various people we could not find a
> >> good
> >> reason for having a VM disk in attached but inactive mode.
> >>
> >> Of course we can wrap the above steps in one step for specific
> >> flows
> >> (add+attach within a VM context for example) but can anyone think
> >> on a
> >> good reason to support attached but inactive disk?
> >>
> >> I would suggest that when attaching a disk to a VM it becomes part
> >> of
> >> the VM (active) like in 'real' machines.
> > 
> > so hotunplug would make the disk floating, as it will detach it as
> > well?
> 
> In short - yes.
> 
> The user will be able to attach/detach disk, the implementation would
> be
> to hotplug or simply plug according to the VM status (up or not) .


What about disks with snapshots?
By the current design of floating disks, detaching a disk with snapshots
can be done only by collapsing and marking the snapshots as broken.
Thus, removing a disk momentarily might be problematic without Plugged/Unplugged status.

Maybe we should keep the current Activate/Deactivate buttons for disks in addition to 
encapsulating attach/detach and plug/unplug commands. 
So, adding/attaching a new disk will plug the disk automatically while allowing the user
deactivating a disk temporarily.


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