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From Marcus Sorensen <shadow...@gmail.com>
Subject Re: [DISCUSS] pause VM
Date Mon, 08 Apr 2013 23:19:43 GMT
Oh yes, I know these things, but here's my point. You said:

"When CloudStack takes a snapshot of volume, it already utilizes snapshot
feature provided by hypervisor to allow taking point of time storage image
in a safe manner from operating system point of view."

What about five volumes? Can we ensure they are all snapshotted at that
same point in time without also pausing the VM, in addition to using those
hypervisor-provided features?  For example, let's say the VM is using a
volume manager and striping data across five data disks, we absolutely have
to take all data disk snapshots at the same point in such a scenario. We of
course have to rely on the user to tell us that they want this, but we
should have the capability.

If we already have a VM snapshot feature that does every connected disk
simultaneously while the VM is suspended, or the hypervisor can do it for
us by quickly pausing/snapshotting/resuming seamlessly then fine, that's
great. It just didn't seem like that functionality existed now, so I was
wondering if anyone is working on it.

That aside, it seems like all of the hypervisors CS controls provide their
own UI to pause a VM. Is it something that has been discussed?




On Mon, Apr 8, 2013 at 4:16 PM, Kelven Yang <kelven.yang@citrix.com> wrote:

>
>
> On 4/8/13 1:39 PM, "Marcus Sorensen" <shadowsor@gmail.com> wrote:
>
> >Has anyone put together a suggestion for adding a 'paused' state to
> >virtual
> >machines? Or is anyone working on it? This seems fairly straightforward,
> >and I think we may need the functionality going forward. Even if people
> >rarely use it themselves, if storage solutions are going to offer
> >snapshots
> >they may want to pause the VM in order to get an atomic snapshot if the VM
> >has multiple disks. So at least internally it may be a useful utility.
>
> Pause VM itself can not ensure data integrity. True data integrity can't
> be ensured without participant of guest OS and related application (for
> example, Microsoft offers Volume Shadow Copy Service to orchestrate and
> allow applications to participate the process via a set of tools and API
> interaction to achieve that).
>
> When CloudStack takes a snapshot of volume, it already utilizes snapshot
> feature provided by hypervisor to allow taking point of time storage image
> in a safe manner from operating system point of view. The ability of
> pausing VM is not mandatory in this case, although pausing/resuming VM may
> be useful in certain use case, it does not seem to be in any urgency or
> fit naturally in general cloud-operations.
>
> -Kelven
>
> >
>
>

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