Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM

Alexander Graf
2009-10-23T11:10:30Z

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On 23.10.2009, at 12:41, MORITA Kazutaka wrote:

> On Fri, Oct 23, 2009 at 12:30 AM, Avi Kivity <avi@redhat.com> wrote:
>
>> 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?
>
> Sheepdog uses consistent hashing to decide where objects store; I/O
> load is balanced across the nodes. When a new node is added or the
> existing node is removed, the hash table changes and the data
> automatically and transparently are moved over nodes.
>
> We plan to implement a mechanism to distribute the data not randomly
> but intelligently; we could use machine load, the locations of VMs,
> etc.

What exactly does balanced mean? Can it cope with individual nodes
having more disk space than others?

>> Do you support multiple guests accessing the same image?
>
> A VM image can be attached to any VMs but one VM at a time; multiple
> running VMs cannot access to the same VM image.

What about read-only access? Imagine you'd have 5 kvm instances each
accessing it using -snapshot.

Great project btw!

Alex

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