[one-users] Restarting a vm instance after shutdown?

[Carlos Martín Sánchez]

Hi Lars,

We think the model you are describing will be easily achieved in the
upcoming 3.0 [1] release.
The approach we are taking to implement persistent VM is making the VM
Template the main VM entity, as you pointed out.


With the new VM Template pool, you will be able to:

(a) A vm instance would start with its own copy of a disk image.
>

A new 'oneimage clone' command will provide a personal private copy of
another Image. Then, a VM Template using that Image can be registered using
'onetemplate create my_vm.one'


> (b) Shutdown would not delete the image.
>

The data won't be lost if the Image is persistent. Which I think is a
reasonable default for an Image created from 'oneimage clone'.


> (c) Some command (restart, or resubmit, or something) would allow one
> to restore a vm instance that had been shut down.
>

A VM instance will finish it's life-cycle after shutdown, this won't change.
But the VM Template will be still available in the pool, and can be
instantiated many more times.


> (d) Disk data would only be discarded with an explicit "delete".
>

There will a explicit delete for the disks (oneimage delete), and for the VM
Template (onetemplate delete).


Best regards,
Carlos.

[1] http://blog.opennebula.org/?p=1626

--
Carlos Martín, MSc
Project Major Contributor
OpenNebula - The Open Source Toolkit for Cloud Computing
www.OpenNebula.org <http://www.opennebula.org/> | cmartin at opennebula.org


On Tue, May 24, 2011 at 10:08 PM, Lars Kellogg-Stedman <
lars at seas.harvard.edu> wrote:

> Steffen, Tino,
>
> Thank you both for your answers.  Using persistent disk images (or the
> "save as" feature) helps a little bit, but what I was really hoping
> for was a model in which:
>
> (a) A vm instance would start with its own copy of a disk image.
> (b) Shutdown would not delete the image.
> (c) Some command (restart, or resubmit, or something) would allow one
> to restore a vm instance that had been shut down.
> (d) Disk data would only be discarded with an explicit "delete".
>
> Ideally, this would be controlled at the virtual machine level, not
> the disk image level.  That is, one would set the "don't delete on
> shutdown" option on the vm instance.
>
> The problem with "persistent" images is that -- as far as I can tell
> -- the vm instance references the image in the repository directly,
> rather than getting "private" persistent *copy* of the image.  The
> problem with "saving" a vm instance is that it doesn't really address
> the problem of, "whoops, I typed the wrong vm id and shutdown the
> wrong system".  It also forces the template description file to become
> more important, since the "recovery" process is to create a new
> virtual machine instance, rather than rebooting the old one.
>
> I have seen several similar questions on the list from folks looking
> for a way to support persistent virtual machines, so it looks as if
> this is a model for which there is some demand.  For those of you
> familiar with the codebase, does this look as if it would be hard to
> implement?  If I wanted to implement it myself, should I be looked at
> the 2.4 code?  We're running 2.2 locally, but I understand that 2.4 is
> on the horizon.
>
> --
> Lars Kellogg-Stedman <lars at seas.harvard.edu>
> Senior Technologist
> Harvard University SEAS
> Academic and Research Computing (ARC)
> _______________________________________________
> Users mailing list
> Users at lists.opennebula.org
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>
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