QoS is your solution. Here a few url's, which explain the concepts
http://ucstech.blogspot.ch/2011/06/qos-on-ucs.html
http://bradhedlund.com/2010/09/15/vmware-10ge-qos-designs-cisco-ucs-nexus/
http://www.cisco.com/c/en/us/support/docs/servers-unified-computing/ucs-2104xp-fabric-extender/110509-ucs-qos-00.html
http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/sw/gui/config/guide/2-0/b_UCSM_GUI_Configuration_Guide_2_0/b_UCSM_GUI_Configuration_Guide_2_0_chapter_010011.pdf
Walter.