On Tue, 2014-03-11 at 06:35 +0000, Bohai (ricky) wrote: > > -----Original Message----- > > From: Jay Pipes [mailto:jaypi...@gmail.com] > > Sent: Tuesday, March 11, 2014 3:20 AM > > To: openstack-dev@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.
Hi Ricky, I guess we will just have to disagree about the relative usefulness of this kind of thing for users of the cloud (and not users of traditional managed hosting) :) Like I said, if it does not affect the performance of other tenants' instances, I'm fine with adding the functionality in a way that is generic (not hypervisor-specific). Best, -jay _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev