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From David Chamard <da...@cloud.ca>
Subject Re: First review of RBD support for primary storage
Date Fri, 29 Jun 2012 17:41:38 GMT
Wido,

Very nice to see. Is there any plan to support xen/xcp hypervisors in the
future?

On Fri, Jun 29, 2012 at 1:39 PM, David Nalley <david@gnsa.us> wrote:

> On Fri, Jun 29, 2012 at 11:59 AM, Wido den Hollander <wido@widodh.nl>
> wrote:
> > Hi,
> >
> > After a couple of months worth of work I'm happy to announce that the RBD
> > support for primary storage in CloudStack seems to be reaching a point
> where
> > it's good enough to be reviewed.
> >
> > If you are planning to test RBD, please do read this e-mail carefully
> since
> > there are still some catches.
> >
> > Although the code inside CloudStack doesn't seem like a lot of code, I
> had
> > to modify code outside CloudStack to get RBD support working:
> >
> > 1. RBD storage pool support in libvirt. [0] [1]
> > 2. Fix a couple of bugs in the libvirt-java bindings. [2]
> >
> > With those issues addressed I could implement RBD inside CloudStack.
> >
> > While doing so I ran into multiple issues inside CloudStack which delayed
> > everything a bit.
> >
> > Now, the RBD support for primary storage knows limitations:
> >
> > - It only works with KVM
> >
> > - You are NOT able to snapshot RBD volumes. This is due to CloudStack
> > wanting to backup snapshots to the secondary storage and uses 'qemu-img
> > convert' for this. That doesn't work with RBD, but it's also very
> > inefficient.
> >
> > RBD supports native snapshots inside the Ceph cluster. RBD disks also
> have
> > the potential to reach very large sizes. Disks of 1TB won't be the
> > exception. It would stress your network heavily. I'm thinking about
> > implementing "internal snapshots", but that is step #2. For now no
> > snapshots.
> >
> > - You are able create a template from a RBD volume, but creating a new
> > instance with RBD storage from a template is still a hit-and-miss.
> Working
> > on that one.
> >
> > Other than these limitations, everything works. You can create instances
> and
> > attach RBD disks. It also supports cephx authorization, so no problem
> there!
> >
> > What do you need to run this patch?
> > - A Ceph cluster
> > - libvirt with RBD storage pool support (>0.9.12)
> > - Modified libvirt-java bindings (jar is in the patch)
> > - Qemu with RBD support (>0.14)
> > - A extra field "user_info" in the storage pool table, see the SQL
> change in
> > the patch
> >
> > You can fetch the code on my Github account [3].
> >
> > Warning: I'll be rebasing against the master branch regularly, so be
> aware
> > of git pull not always working nicely.
> >
> > I'd like to see this code reviewed while I'm working on the latest stuff
> and
> > getting all the patches upstream in other projects (mainly the libvirt
> Java
> > bindings).
> >
> > Any suggestions or comments?
> >
> > Thank you!
> >
> > Wido
> >
> >
> > [0]:
> >
> http://libvirt.org/git/?p=libvirt.git;a=commit;h=74951eadef85e2d100c7dc7bd9ae1093fbda722f
> > [1]:
> >
> http://libvirt.org/git/?p=libvirt.git;a=commit;h=122fa379de44a2fd0a6d5fbcb634535d647ada17
> > [2]: https://github.com/wido/libvirt-java/commits/cloudstack
> > [3]: https://github.com/wido/CloudStack/commits/rbd
>
>
>
> Wido,
>
> I am thrilled to see Ceph support at this stage. Hopefully I'll get to
> try this out next week.
> Any chance you'd consider putting this in a topic branch in the ASF repo?
>
> --David
>

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