The M420 only has 2 external USB ports and is not recommended to run an OS from a USB externally.   The M620 does have an internal USB slot.  However, Dell does not support running an OS from a USB key. The only validated and supported method is from the SD card. Here is a list of validated USB keys from VMWare: [URL] From this list, the Kingston Data Traveler is the only recommended key in our servers. Regards,  
Does anyone have specs on the internal USB support for M420 or M620 blades? I know the manual reads, "CAUTION: To avoid interference with other components in the blade, the maximum allowable dimensions of the
Internal USB on M420 or M620 blades