Re: QoS
In a hyper converged environment you probably wouldn't need to or be able to implement QOS at the storage layer, with HC you essentially have an appliance to the hypervisor and so have limited use cases outside meaning QOS is probably best implemented at that level.
To implement Storage QOS succesfully you need a detailed understanding of the underlying storage hardware and connecting infrastructure, which in a HC environment is likely just a bunch of disks with a DAS attachment and maybe some network based mirroring for H/A. Which means you don't really have an end to end picture of all the performance dependencies, you're really just handing everything off to the driver stack which simply forwards to the next in line.
If you have to take a broader view and say I need this storage to support more than just my VM's then storage based QOS is very useful. It's highly likely the non VM stuff will prove to be the noisy neighbour (that's why it aint a VM), in which case you'll need a common method of providing QOS outside the hypervisor. If you don't have that capability then you have to start building performance silo's, which come to think of it seems to be what a lot of SDS is about (DAS for the new century).