[ceph-users] features required for live migration

Jason Dillaman jdillama at redhat.com
Tue Nov 14 07:36:45 PST 2017


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


More information about the ceph-users mailing list