Yes, drives on the UCS servers are hot-swappable:
http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/c/hw/C220/install/C220/overview.html
http://www.cisco.com/c/en/us/products/collateral/servers-unified-computing/ucs-c220-m3-rack-server/data_sheet_c78-700626.html