[Sheepdog] Sheep gateway question

[MORITA Kazutaka]

At Wed, 9 Nov 2011 09:27:53 -0000,
Matthew Law wrote:
> 
> On Wed, November 9, 2011 3:10 am, MORITA Kazutaka wrote:
> > Different VMs can use different gateways, so if there are many VMs,
> > the gateway cannot be a bottleneck.  Our goal is not to provide the
> > combined bandwidth of many disks to one VM, but rather to achieve
> > scalability; Sheepdog provides enough bandwidth to each VM even if
> > many VMs use Sheepdog at the same time.
> 
> How is the gateway node decided?  Perhaps we could add this to the
> documentation to explain to anyone who jumped to the same (wrong!)
> conclusion as me? :-)

You can specify it with qemu command line arguemnts.  It is
localhost:7000 by default.

See also:
  https://github.com/collie/qemu/blob/master/qemu-options.hx#L1796

> 
> I think for my use case and for the majority of people 'enough bandwidth'
> is simply that the VMs do not 'feel' slow when reading and writing and
> that I/O is predictable.  Nobody can expect clustered storage of this type
> to perform like a high performance disk array (this is not the use case). 
> If it scales well, performs predictably and I/O latency is acceptable then
> I think it will appeal to many.
> 
> Perhaps the sheepdog home page could add a section something like this:
> 
> You should consider Sheepdog if you are looking for clustered storage that:
> 
>   * Is 'scale-out', with no single point of failure
>   * Is simple to setup and use (secured at the network layer)
>   * Is compatible with KVM via QEmu (Xen support is coming later...)
>   * Works at the block-level
>   * ...
> 
> You should not consider Sheepdog if you are looking for:
> 
>   * High bandwidth/low latency storage ('scale-up')
>   * Fine grained authentication and authorization of storage nodes
>   * Works at the file level (clustered file system)
>   * Tiering
>   * ...
> 
> Just a suggestion.

Thanks!  I've added those description to Sheepdog top page:

  http://www.osrg.net/sheepdog/


Thanks,

Kazutaka

> 
> Thanks,
> 
> Matt.
> 
> 
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