On Tue, Sep 18, 2018 at 03:07:45PM +0200, Attila Fazekas wrote: > On Tue, Sep 18, 2018 at 2:09 PM, Peter Penchev <openstack-...@storpool.com> > wrote: > > > 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. > > > > Cinder might get a feature for `rescue` a volume in case accidentally > someone > deleted the DB record or some other bad thing happened. > This needs to be admin only op where you would need to specify where is the > volume, > If just a new volume `shows up` on the storage, but without > the knowledge of cinder, it could be rescued as well.
Hmm, is this not what the Cinder "manage" command does? > Among same storage types probably cinder could have an admin only > API for transfer. > > I am not sure is volume backup/restore is really better across regions > than the above steps properly piped however > it is very infrastructure dependent, > bandwidth and latency across regions matters. [snip discussion] Well, the reason my initial message said "assume the underlying storage can do that" was that I did not want to go into marketing/advertisement territory and say flat out that the StorPool storage system can do that :) 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
