[Sheepdog] Block write size

[MORITA Kazutaka]

At Fri, 16 Dec 2011 17:10:19 +0800,
Liu Yuan wrote:
> 
> On 12/16/2011 04:57 PM, John Ryan wrote:
> 
> > Ok I got it. All writes have all or nothing semantics. What happens to
> > writes that straddle chunks? How is that case handled? Because you could
> > be writing to two different set of replicas.
> > 
> 
> 
> read/write requests are firstly handled in the qemu block layer. I guess
> request that straddle chunks will be split into several ones. Kazum,
> would you confirm this?

Yes, qemus send several requests in the such case.  It is no problem
even if only one of the requests would fail.  It is because the qemu
receives an EIO error in the scenario and we don't need to make any
assumption about the data written.

Thanks,

Kazutaka