Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm

[Avi Kivity]

On 05/25/2010 02:02 PM, Kevin Wolf wrote:
> > > So could we not standardize a protocol for this that both sheepdog and
> > > ceph could implement?
> > >        
> > The protocol already exists, nbd.  It doesn't support snapshotting etc.
> > but we could extend it.
> >
> > But IMO what's needed is a plugin API for the block layer.
> >      
> What would it buy us, apart from more downstreams and having to maintain
> a stable API and ABI?

Currently if someone wants to add a new block format, they have to 
upstream it and wait for a new qemu to be released.  With a plugin API, 
they can add a new block format to an existing, supported qemu.

> Hiding block drivers somewhere else doesn't make
> them stop existing, they just might not be properly integrated, but
> rather hacked in to fit that limited stable API.
>    

They would hack it to fit the current API, and hack the API in qemu.git 
to fit their requirements for the next release.

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