[sheepdog] consistency problem when replicating to multi-replica

[guping]

Sheepdog send write request to all replica simultaneously to do the 
replication. Which I think could lead to divergent content in replicas.

Imagine a scenario, there are two write requests A & B to update the 
same offset in a 2-replicas object. If a qemu client send A and B to a 
gateway concurrently, the gateway will send A and B to the same set of 
replicas simultaneously. Which could not guarantee the same sequence to 
apply A and B, you can apply A then B in a replica and apply B then A in 
another replica, then you get two request return successfully but not 
the same data in the replicas.

Is this a consistency problem in sheepdog? How can we deal with it?

-- 
Thanks,
Gu Ping