Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication]

[Paolo Bonzini]

Il 31/05/2012 10:44, Roni Luxenberg ha scritto:
> a continuous replication application expects to get all IOs in the same order 
> as
> issued by the guest irrespective of the (rate of the) flushes done within the 
> guest.

Does real hardware give such consistency, unless you disable caching?

> This is required to be able to support more advanced features like cross VM 
> consistency
> where the application protects a group of VMs (possibly running on different 
> hosts)
> forming a single logical application/service.
> Does the design strictly maintain this property?

No.  But this is only a problem with the implementation, not with the API.

> under this design and assuming async implementation, is a same block
> that is written few times in a raw by the guest guaranteed to be
> received by the continuous replication agent the same exact number of
> times without overriding any of the writes?

No.

Paolo