When I use my large capacity USB thrumb drive to flash / update FW or save the system service report, the USB drive is not detected.

We support many sizes and manufactures USB flash drives, please see the Promise VessRAID SR3 Compatibility List at:

http://www.promise.com/mediabank/Download%20Bank/Compatibility/VessJBOD%201000%20Series%20SR3%20Compatibility%20List%20V1.0-20100520.pdf