On Fri, Jun 29, 2012 at 11:59 AM, Wido den Hollander <w...@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
