[ovirt-users] oVirt 3.6 SLA and QoS algorithm

Hello! We are using oVirt 3.6 in our infrastructure and storage QoS in passive state (they are configured but not applie) for some of the servers. Last time we needed to activate QoS on high load servers and it caused storage load decrease. And this situation has raised some questions: 1. What happened to overlimit storage traffic, when QoS applying on high load virtual machine: a) All over traffic is pulling into some queue, where all disk transactions can be successfully finished with QoS throughput? b) All over-limitation data is dropped and opened transactions failed? c) All active transactions finishes on speed beyond QoS, but all new transactions immediately start to work based on configured limits? 2. How QoS mechanism actually works? Does it use some oVirt specific functions or it uses some system features to limit storage, network or CPU usage? If system one, then the QoS are provided by libvirt (using virsh or directly) or system kernel options and which one? Thanks in advance!