The real DESCRIPTION field here is just the auto-generated stub "Cisco UCS fabric:FcSanEp:fillPattern managed object property", so it carries no real prose -- but the property name and its CucsFabricFillPattern type tell you what it holds: It holds the FC idle/fill-word pattern that has been negotiated on this FC SAN uplink port's link -- either the older "ARBFF" pattern or the newer "IDLE" pattern used at higher FC speeds. This matters specifically for FC links because the two ends of the upstream Fibre Channel SAN switch port (an MDS or Nexus) it is cabled to must agree on the fill pattern for the link to initialize cleanly at speeds of 8Gbps and above; a mismatch here on this FC SAN uplink port is a classic cause of a link that will not come up even though both SFPs look fine. A healthy 16Gbps link on this FC SAN uplink port would typically show "idle", while an older 2Gbps or 4Gbps link might still negotiate "arbff".