Hello. The VRTX chassis can be powered with 2 power supplies, PS1 &PS2 while still maintaining redundancy. They are located on the top bays of the chassis. However, due to acoustics, it is recommended to utilize all the 4 power supplies. See Users' Guide for more information: [URL] 
I have a VRTX with two M520 blades, and 12 2.5in 300GB hard drives with a shared PERC8 controller.  It has four power supplies.  I need to know if two power supplies will keep it running.   Does anyone know, or can anyone tell me how to verify it without testing live?  Thanks.
VRTX Power Supply Question