[Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM

[Anthony Liguori]

Avi Kivity wrote:
> On 10/21/2009 07:13 AM, MORITA Kazutaka wrote:
> > Hi everyone,
> >
> > Sheepdog is a distributed storage system for KVM/QEMU. It provides
> > highly available block level storage volumes to VMs like Amazon EBS.
> > Sheepdog supports advanced volume management features such as snapshot,
> > cloning, and thin provisioning. Sheepdog runs on several tens or 
> > hundreds
> > of nodes, and the architecture is fully symmetric; there is no central
> > node such as a meta-data server.
>
> Very interesting!  From a very brief look at the code, it looks like 
> the sheepdog block format driver is a network client that is able to 
> access highly available images, yes?
>
> If so, is it reasonable to compare this to a cluster file system setup 
> (like GFS) with images as files on this filesystem?  The difference 
> would be that clustering is implemented in userspace in sheepdog, but 
> in the kernel for a clustering filesystem.

I'm still in the process of reading the code, but that's the impression 
I got too.  It made me think that the protocol for qemu to communicate 
with sheepdog could be a filesystem protocol (like 9p) and sheepdog 
could expose itself as a synthetic.  There are some interesting 
ramifications to something like that--namely that you could mount 
sheepdog on localhost and interact with it through the vfs.

Very interesting stuff, I'm looking forward to examining more closely.

Regards,

Anthony Liguori