Thanks a lot for all your comments,
If you don't see any problem... I will enable the following features that might fit my requirements:
Layering
Striping
Exclusive locking
Object map
Fast-diff
Thanks a lot
Óscar Segarra
2017-11-14 16:56 GMT+01:00 Jason Dillaman <jdillama@xxxxxxxxxx>:
From the documentation [1]:shareableIf present, this indicates the device is expected to be shared between domains (assuming the hypervisor and OS support this), which means that caching should be deactivated for that device.Basically, it's the use-case for putting a clustered file system (or similar) on top of the block device. For the vast majority of cases, you shouldn't enable this in libvirt.--On Tue, Nov 14, 2017 at 10:49 AM, Oscar Segarra <oscar.segarra@xxxxxxxxx> wrote: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....Thanks a lot.2017-11-14 16:36 GMT+01:00 Jason Dillaman <jdillama@xxxxxxxxxx>:On Tue, Nov 14, 2017 at 10:25 AM, Oscar Segarra <oscar.segarra@xxxxxxxxx> 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@xxxxxxxxxx>:
>>
>> 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@xxxxxxxxxxx> 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@xxxxxxxx>:
>> >>
>> >> 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@xxxxxxxxxxxxxx
>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>> >
>> >
>> >
>> > _______________________________________________
>> > ceph-users mailing list
>> > ceph-users@xxxxxxxxxxxxxx
>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>> >
>>
>>
>>
>> --
>> Jason
>
>
Jason
Jason
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