On Tue, Sep 18, 2018 at 11:32:37AM +0200, Attila Fazekas wrote: [format recovered; top-posting after an inline reply looks confusing] > On Mon, Sep 17, 2018 at 11:43 PM, Jay Pipes <jaypi...@gmail.com> wrote: > > > On 09/17/2018 09:39 AM, Peter Penchev wrote: > > > >> Hi, > >> > >> So here's a possibly stupid question - or rather, a series of such :) > >> Let's say a company has two (or five, or a hundred) datacenters in > >> geographically different locations and wants to deploy OpenStack in both. > >> What would be a deployment scenario that would allow relatively easy > >> migration (cold, not live) of instances from one datacenter to another? > >> > >> My understanding is that for servers located far away from one another > >> regions would be a better metaphor than availability zones, if only > >> because it would be faster for the various storage, compute, etc. > >> services to communicate with each other for the common case of doing > >> actions within the same datacenter. Is this understanding wrong - is it > >> considered all right for groups of servers located in far away places to > >> be treated as different availability zones in the same cluster? > >> > >> If the groups of servers are put in different regions, though, this > >> brings me to the real question: how can an instance be migrated across > >> regions? Note that the instance will almost certainly have some > >> shared-storage volume attached, and assume (not quite the common case, > >> but still) that the underlying shared storage technology can be taught > >> about another storage cluster in another location and can transfer > >> volumes and snapshots to remote clusters. From what I've found, there > >> are three basic ways: > >> > >> - do it pretty much by hand: create snapshots of the volumes used in > >> the underlying storage system, transfer them to the other storage > >> cluster, then tell the Cinder volume driver to manage them, and spawn > >> an instance with the newly-managed newly-transferred volumes > >> > > > > Yes, this is a perfectly reasonable solution. In fact, when I was at AT&T, > > this was basically how we allowed tenants to spin up instances in multiple > > regions: snapshot the instance, it gets stored in the Swift storage for the > > region, tenant starts the instance in a different region, and Nova pulls > > the image from the Swift storage in the other region. It's slow the first > > time it's launched in the new region, of course, since the bits need to be > > pulled from the other region's Swift storage, but after that, local image > > caching speeds things up quite a bit. > > > > This isn't migration, though. Namely, the tenant doesn't keep their > > instance ID, their instance's IP addresses, or anything like that.
Right, sorry, I should have clarified that what we're interested in is technically creating a new instance with the same disk contents, so that's fine. Thanks for confirming that there is not a simpler way that I've missed, I guess :) > > I've heard some users care about that stuff, unfortunately, which is why > > we have shelve [offload]. There's absolutely no way to perform a > > cross-region migration that keeps the instance ID and instance IP addresses. > > > > - use Cinder to backup the volumes from one region, then restore them to > >> the other; if this is combined with a storage-specific Cinder backup > >> driver that knows that "backing up" is "creating a snapshot" and > >> "restoring to the other region" is "transferring that snapshot to the > >> remote storage cluster", it seems to be the easiest way forward (once > >> the Cinder backup driver has been written) > >> > > > > Still won't have the same instance ID and IP address, which is what > > certain users tend to complain about needing with move operations. > > > > - use Nova's "server image create" command, transfer the resulting > >> Glance image somehow (possibly by downloading it from the Glance > >> storage in one region and simulateneously uploading it to the Glance > >> instance in the other), then spawn an instance off that image > >> > > > > Still won't have the same instance ID and IP address :) > > > > Best, > > -jay > > > > The "server image create" approach seems to be the simplest one, > >> although it is a bit hard to imagine how it would work without > >> transferring data unnecessarily (the online articles I've seen > >> advocating it seem to imply that a Nova instance in a region cannot be > >> spawned off a Glance image in another region, so there will need to be > >> at least one set of "download the image and upload it to the other > >> side", even if the volume-to-image and image-to-volume transfers are > >> instantaneous, e.g. using glance-cinderclient). However, when I tried > >> it with a Nova instance backed by a StorPool volume (no ephemeral image > >> at all), the Glance image was zero bytes in length and only its metadata > >> contained some information about a volume snapshot created at that > >> point, so this seems once again to go back to options 1 and 2 for the > >> different ways to transfer a Cinder volume or snapshot to the other > >> region. Or have I missed something, is there a way to get the "server > >> image create / image download / image create" route to handle volumes > >> attached to the instance? > >> > >> So... have I missed something else, too, or are these the options for > >> transferring a Nova instance between two distant locations? > >> > >> Thanks for reading this far, and thanks in advance for your help! > >> > >> Best regards, > >> Peter > > Create a volume transfer VM/machine in each region. > attache the volume -> dd -> compress -> internet ->decompress -> new > volume, attache(/boot with) to the volume to the final machine. > In case you have frequent transfers you may keep up the machines for the > next one.. Thanks for the advice, but this would involve transferring *a lot* more data than if we leave it to the underlying storage :) As I mentioned, the underlying storage can be taught about remote clusters and can be told to create a remote snapshot of a volume; this will be the base on which we will write our Cinder backup driver. So both my options 1 (do it "by hand" with the underlying storage) and 2 (cinder volume backup/restore) would be preferable. > In case the storage is just on the compute node: snapshot ->glance download > ->glance upload Right, as I mentioned in my description of the third option, this does not really work with attached volumes (thus your "just on the compute node") and as I mentioned before listing the options, the instances will almost certainly have attached volumes. > Would be nice if cinder/glance could take the credentials for another > openstack and move the volume/image to another cinder/glance. > > If you want the same IP , specify the ip at instance boot time (port > create), > but you cannot be sure the same ip is always available or really route-able > to different region.. unless... VPN like solution in place... > > The uuid not expected to be changed by the users or admins (unsafe), > but you can use other metadata for description/your uuid. Best regards, Peter -- Peter Penchev openstack-...@storpool.com https://storpool.com/ _______________________________________________ Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack Post to : openstack@lists.openstack.org Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
