---USB Ports enable access to USB flash memory devices for software image loading and recovery.
---3 USB ports: 2 host and 1 device port for peripheral devices
Check below link for more info:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/hw/nexus7000/installation/guide/n7k_hig_book/n7k_replacing.html
Regards,
Naveen
****Rate if it is helpful****