[ceph-users] features required for live migration

Oscar Segarra oscar.segarra at gmail.com
Tue Nov 14 07:49:23 PST 2017


Hi Jason,

The big use-case for sharing a block device is if you set up a clustered
file system on top of it, and I'd argue that you'd probably be better off
using CephFS.
--> Nice to know!

Thanks a lot for your clarifications, in this case I referenced the
shareable flag that one can see in the KVM. I'd like to know the suggested
configuration for rbd images and live migration....

[image: Imágenes integradas 1]

Thanks a lot.

2017-11-14 16:36 GMT+01:00 Jason Dillaman <jdillama at redhat.com>:

> On Tue, Nov 14, 2017 at 10:25 AM, Oscar Segarra <oscar.segarra at gmail.com>
> wrote:
> > In my environment, I have a Centos7 updated todate.... therefore, all
> > features might work as expected to do...
> >
> > Regarding the other question, do you suggest making the virtual disk
> > "shareable" in rbd?
>
> Assuming you are refering to the "--image-shared" option when creating
> an image, the answer is no. That is just a short-cut to disable all
> features that depend on the exclusive lock. The big use-case for
> sharing a block device is if you set up a clustered file system on top
> of it, and I'd argue that you'd probably be better off using CephFS.
>
> > Thanks a lot
> >
> > 2017-11-14 15:58 GMT+01:00 Jason Dillaman <jdillama at redhat.com>:
> >>
> >> Concur -- there aren't any RBD image features that should prevent live
> >> migration when using a compatible version of librbd. If, however, you
> >> had two hosts where librbd versions were out-of-sync and they didn't
> >> support the same features, you could hit an issue if a VM with fancy
> >> new features was live migrated to a host where those features aren't
> >> supported since the destination host wouldn't be able to open the
> >> image.
> >>
> >> On Tue, Nov 14, 2017 at 7:55 AM, Cassiano Pilipavicius
> >> <cassiano at tips.com.br> wrote:
> >> > Hi Oscar, exclusive-locking should not interfere with live-migration.
> I
> >> > have
> >> > a small virtualization cluster backed by ceph/rbd and I can migrate
> all
> >> > the
> >> > VMs which RBD image have exclusive-lock enabled without any issue.
> >> >
> >> >
> >> >
> >> > Em 11/14/2017 9:47 AM, Oscar Segarra escreveu:
> >> >
> >> > Hi Konstantin,
> >> >
> >> > Thanks a lot for your advice...
> >> >
> >> > I'm specially interested in feature "Exclusive locking". Enabling this
> >> > feature can affect live/offline migration? In this scenario
> >> > (online/offline
> >> > migration)  I don't know if two hosts (source and destination) need
> >> > access
> >> > to the same rbd image at the same time
> >> >
> >> > It looks that enabling Exlucisve locking you can enable some other
> >> > interessant features like "Object map" and/or "Fast diff" for backups.
> >> >
> >> > Thanks a lot!
> >> >
> >> > 2017-11-14 12:26 GMT+01:00 Konstantin Shalygin <k0ste at k0ste.ru>:
> >> >>
> >> >> On 11/14/2017 06:19 PM, Oscar Segarra wrote:
> >> >>
> >> >> What I'm trying to do is reading documentation in order to understand
> >> >> how
> >> >> features work and what are they for.
> >> >>
> >> >> http://tracker.ceph.com/issues/15000
> >> >>
> >> >>
> >> >> I would also be happy to read what features have negative sides.
> >> >>
> >> >>
> >> >> The problem is that documentation is not detailed enough.
> >> >>
> >> >> The proof-test method you suggest I think is not a good procedure
> >> >> because
> >> >> I want to a void a corrpution in the future due to a bad
> configuration
> >> >>
> >> >>
> >> >> So my recommendation: if you can wait - may be from some side you
> >> >> receive
> >> >> a new information about features. Otherwise - you can set minimal
> >> >> features
> >> >> (like '3') - this is enough for virtualization (snapshots, clones).
> >> >>
> >> >> And start your project.
> >> >>
> >> >> --
> >> >> Best regards,
> >> >> Konstantin Shalygin
> >> >
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > ceph-users mailing list
> >> > ceph-users at lists.ceph.com
> >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > ceph-users mailing list
> >> > ceph-users at lists.ceph.com
> >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >> >
> >>
> >>
> >>
> >> --
> >> Jason
> >
> >
>
>
>
> --
> Jason
>
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