The UCS ecosystem leverages a port aggregation solution to chassis I/O, namely, the FEX modules.
The FEX modules are not fully featured switches. Nor do they possess any forwarding policy intelligence at all. Instead, the FEX modules deploy a "pinning" approach in which downlinks (those that face the blade server's NIC's, LOMs, mezzanine cards) are mapped to an uplink port (those that face a 6100 Fabric Interconnect) to form what can be described as an aggregator group.
The result is a simplified approach to blade I/O in which the traffic patterns are predictable and failover is deterministic. Moreover, there is no need to configure STP because the ports are uplinked in a manner as to preclude any possibility of a bridging loop.
This having been said, is there some merit to the argument that this port aggregation design places a hole in the middle of a QoS deployment since the scheduling of packets on the uplink ports facing the 6100 Fabric Interconnect is not performed in a manner that recognizes priority?
To elaborate a bit more, one can have a VMware deployment and leverage NetIOC or perhaps configure QoS on a 1000v switch (whose uplink ports are mapped to a port on the Palo VIC) and configure QoS on the VIC, and then on the 6100 Fabric Interconnect. But, since the FEX is not scheduling traffic to the 6100 Fabric Interconnect according to any priority, the QoS deployment has a hole in the middle, so to speak.