Open Stack

> -----Original Message-----
> From: Jay Pipes [mailto:jaypipes at gmail.com]
> Sent: Tuesday, March 11, 2014 3:20 AM
> To: openstack-dev at lists.openstack.org
> Subject: Re: [openstack-dev] [nova] a question about instance snapshot
>
> On Mon, 2014-03-10 at 12:13 -0400, Shawn Hartsock wrote:
> > We have very strong interest in pursing this feature in the VMware
> > driver as well. I would like to see the revert instance feature
> > implemented at least.
> >
> > When I used to work in multi-discipline roles involving operations it
> > would be common for us to snapshot a vm, run through an upgrade
> > process, then revert if something did not upgrade smoothly. This
> > ability alone can be exceedingly valuable in long-lived virtual
> > machines.
> >
> > I also have some comments from parties interested in refactoring how
> > the VMware drivers handle snapshots but I'm not certain how much that
> > plays into this "live snapshot" discussion.
>
> I think the reason that there isn't much interest in doing this kind of thing is
> because the worldview that VMs are pets is antithetical to the worldview that
> VMs are cattle, and Nova tends to favor the latter (where DRS/DPM on
> vSphere tends to favor the former).
>
> There's nothing about your scenario above of being able to "revert" an instance
> to a particular state that isn't possible with today's Nova.
> Snapshotting an instance, doing an upgrade of software on the instance, and
> then restoring from the snapshot if something went wrong (reverting) is
> already fully possible to do with the regular Nova snapshot and restore
> operations. The only difference is that the "live-snapshot"
> stuff would include saving the memory view of a VM in addition to its disk state.
> And that, at least in my opinion, is only needed when you are treating VMs like
> pets and not cattle.
>

Hi Jay,

I read every words in your reply and respect what you said.

But i can't agree with you that memory snapshot is a feature for pat not for cattle.
I think it's a feature whatever what do you look the instance as.

The world doesn't care about what we look the instance as, in fact, currently almost all the
mainstream hypervisors have supported the memory snapshot.
If it's just a dispensable feature and no users need it, I can't understand why
the hypervisors provide it without exception.

In the document " OPENSTACK OPERATIONS GUIDE" section " Live snapshots" has the
below words:
" To ensure that important services have written their contents to disk (such as, databases),
we recommend you read the documentation for those applications to determine what commands
to issue to have them sync their contents to disk. If you are unsure how to do this,
 the safest approach is to simply stop these running services normally.
"
This just pushes all the responsibility to guarantee the consistency of the instance to the end user.
It's absolutely not convenient and I doubt whether it's appropriate.


Best regards to you.
Ricky

> Best,
> -jay
>
> > On Mon, Mar 10, 2014 at 12:04 AM, Bohai (ricky) <bohai at huawei.com>
> wrote:
> > >> -----Original Message-----
> > >> From: Alex Xu [mailto:xuhj at linux.vnet.ibm.com]
> > >> Sent: Sunday, March 09, 2014 10:04 PM
> > >> To: OpenStack Development Mailing List (not for usage questions)
> > >> Subject: Re: [openstack-dev] [nova] a question about instance
> > >> snapshot
> > >>
> > >> Hi, Jeremy, the discussion at here
> > >> http://lists.openstack.org/pipermail/openstack-dev/2013-August/0136
> > >> 88.html
> > >>
> > >
> > > I have a great interest in the topic too.
> > > I read the link you provided, and there is a little confusion for me.
> > > I agree with the security consideration in the discussion and memory
> snapshot can't be used for the cloning instance easily.
> > >
> > > But I think it's safe for the using for Instance revert.
> > > And revert the instance to a checkpoint is valuable for the user.
> > > Why we didn't use it for instance revert in the first step?
> > >
> > > Best regards to you.
> > > Ricky
> > >
> > >> Thanks
> > >> Alex
> > >> On 2014年03月07日 10:29, Liuji (Jeremy) wrote:
> > >> > Hi, all
> > >> >
> > >> > Current openstack seems not support to snapshot instance with
> > >> > memory and
> > >> dev states.
> > >> > I searched the blueprint and found two relational blueprint like below.
> > >> > But these blueprint failed to get in the branch.
> > >> >
> > >> > [1]: https://blueprints.launchpad.net/nova/+spec/live-snapshots
> > >> > [2]:
> > >> > https://blueprints.launchpad.net/nova/+spec/live-snapshot-vms
> > >> >
> > >> > In the blueprint[1], there is a comment,"
> > >> > We discussed this pretty extensively on the mailing list and in a
> > >> > design
> > >> summit session.
> > >> > The consensus is that this is not a feature we would like to have in nova.
> > >> --russellb "
> > >> > But I can't find the discuss mail about it. I hope to know why we think
> so ?
> > >> > Without memory snapshot, we can't to provide the feature for user
> > >> > to revert
> > >> a instance to a checkpoint.
> > >> >
> > >> > Anyone who knows the history can help me or give me a hint how to
> > >> > find the
> > >> discuss mail?
> > >> >
> > >> > I am a newbie for openstack and I apologize if I am missing
> > >> > something very
> > >> obvious.
> > >> >
> > >> >
> > >> > Thanks,
> > >> > Jeremy Liu
> > >> >
> > >> >
> > >> > _______________________________________________
> > >> > OpenStack-dev mailing list
> > >> > OpenStack-dev at lists.openstack.org
> > >> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> > >> >
> > >> >
> > >> >
> > >>
> > >>
> > >> _______________________________________________
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> > >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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> >
> >
> >
>
>
>
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