Thanks for writing these down in wiki pages.

Another possible feature would be make each node in the clusters to be able to 
maintain the storage domain master data in parallel without a bottle neck in 
one SPM node.  By this way, the storage domain maintain workload will be 
dispersed into different nodes.

On 2012-6-19 5:09, Saggi Mizrahi wrote:
Ryan, thanks for commenting.

Sadly I feel that your points, though important, are a bit of a digression from 
the main discussion.
Internal architectural changes to VDSM are out of the scope as this should be 
done on a very tight schedual.

Seeing as this is a pretty good list of things that need to be done\discussed 
in VDSM anyway. I took the liberty of putting them in a wiki page [1] so we 
don't forget and others can add\comment on the ideas.

In any case you can feel free to raise those issues on the list separately. 
Specifically, 3rd party plugins might be very topical with the undergoing 
gluster integration work.


----- Original Message -----
From: "Ryan Harper"<>
To: "Saggi Mizrahi"<>
Cc: "VDSM Project Development"<>, "Anthony 
Sent: Monday, June 18, 2012 3:43:42 PM
Subject: Re: [vdsm] [virt-node] VDSM as a general purpose virt host manager

* Saggi Mizrahi<>  [2012-06-18 10:05]:
I would like to put on to the table for descussion the growing need
for a way
to more easily reuse of the functionality of VDSM in order to
service projects
other than Ovirt-Engine.

Originally VDSM was created as a proprietary agent for the sole
purpose of
serving the then proprietary version of what is known as
ovirt-engine. Red Hat,
after acquiring the technology, pressed on with it's commitment to
open source
ideals and released the code. But just releasing code into the wild
build a community or makes a project successful. Further more when
open source software you should aspire to build reusable components
instead of
monolithic stacks.


Thanks for sending this out.  I've been trying to pull together some
thoughts on what else is needed for vdsm as a community.  I know that
for some time downstream has been the driving force for all of the
and now with a community there are challenges in finding our own way.

While we certainly don't want to make downstream efforts harder, I
we need to develop and support our own vision for what vdsm can be
some what independent of downstream and other exploiters.

Revisiting the API is definitely a much needed endeavor and I think
adding some use-cases or sample applications would be useful in
demonstrating whether or not we're evolving the API into something
easier to use for applications beyond engine.

We would like to expose a stable, documented, well supported API.
This gives
us a chance to rethink the VDSM API from the ground up. There is
already work
in progress of making the internal logic of VDSM separate enough
from the API
layer so we could continue feature development and bug fixing while
the API of the future.

In order to achieve this though we need to do several things:
    1. Declare API supportability guidelines
    2. Decide on an API transport (e.g. REST, ZMQ, AMQP)
    3. Make the API easily consumable (e.g. proper docs, example
    code, extending
       the API, etc)
    4. Implement the API itself
I agree with the list, but I'd like to work on the redesign
discussion so
that we're not doing all of 1-4 around the existing API that's

I'm over due for posting a feature page on vdsm standalone mode, and
have some other thoughts on various uses.

Some other paths of thought for use-cases I've been mulling over:

     - Simplifying using QEMU/KVM
         - consuming qemu via command line
             - can we manage/support developers launching qemu
         - consuming qemu via libvirt
             - can we integrate with systems that are already using

     - Addressing issues with libvirt
         - are there kvm specific features we can exploit that libvirt

     - Scale-up/fail-over
         - can we support a single vdsm node, but allow for building
         clusters/groups without bringing in something like
         - can we look at decentralized fail-over for reliability
         a central mgmt server?

     - pluggability
         - can we support an API that allows for third-party plugins
         support new features or changes in implementation?

     - kvm tool integration into the API
         - there are lots of different kvm virt tools for various
         and they are all stand-alone tools.  Can we integrate their
         use into the node level API.  Think libguestfs, virt-install,
         p2v/v2v tooling.  All of these are available, but there isn't
         easy way to use this tools through an API.

     - host management operations
         - vdsm already does some host level configuration (see
               networking e.g.) it would be good to think about
         the API to cover other areas of configuration and updates
             - hardware enumeration
             - driver level information
             - storage configuration
                 (we've got a bit of a discussion going around
                  libstoragemgmt here)

     - performance monitoring/debugging
         - is the host collecting enough information to do debug/perf
         - can we support specific configurations of a host that
         for specific workloads
             - and can we do this in the API such that third-parties
             supply and maintain specific workload configurations

All of these are dependent on one another and the permutations are
This is why I think we should try and work on each one separately.
discussions will be done openly on the mailing list and until the
final version
comes out nothing is set in stone.

If you think you have anything to contribute to this process,
please do so
either by commenting on the discussions or by sending
patches. Once the API solidifies it will be quite difficult to
fundamental things, so speak now or forever hold your peace. Note
that this is
just an introductory email. There will be a quick follow up email
to kick start
the discussions.

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Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx

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Shu Ming<>
IBM China Systems and Technology Laboratory

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