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 <jdill...@redhat.com>: > On Tue, Nov 14, 2017 at 10:25 AM, Oscar Segarra <oscar.sega...@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 <jdill...@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 > >> <cassi...@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 <k0...@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@lists.ceph.com > >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > >> > > >> > > >> > > >> > _______________________________________________ > >> > ceph-users mailing list > >> > ceph-users@lists.ceph.com > >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > >> > > >> > >> > >> > >> -- > >> Jason > > > > > > > > -- > Jason >
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