What is QFabric?

It is that creates a single logical switch that connects the entire data center rather than tiers of multiple access aggregation and core switches.

BACKGROUND: Juniper leapfrogs Cisco with QFabric data center product blitz

Why is that an advantage?

It improves performance by reducing latency, which is accomplished by getting rid of layers of switches and cutting the number of devices needed, which also reduces the demand for space and power as well as management and maintenance.