Hi Stefan,Please check the link contain information on FlexFlash SD Card Support.http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/2.1/b_UCSM_GUI_Configuration_Guide_2_1_chapter_0110001.html

Please use this link may be this will help you.http://www.cisco.com/en/US/docs/unified_computing/ucs/c/sw/cli/config/guide/1.4.1/b_Cisco_UCS_C-Series_CLI_Configuration_Guide_141_chapter_01101.html

Please check this link hope it may help.http://www.cisco.com/en/US/prod/collateral/ps10265/ps10493/C240M3_LFF_SpecSheet.pdf