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

[Avi Kivity]

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.

How is load balancing implemented?  Can you move an image transparently 
while a guest is running?  Will an image be moved closer to its guest?  
Can you stripe an image across nodes?

Do you support multiple guests accessing the same image?

What about fault tolerance - storing an image redundantly on multiple nodes?

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