If used with following hard drive ND2725 cannot work with SONY EX1/EX3.
* Not compatible
1) All Samsung hard drive
2) All Western Digital hard drive

Following hard drives are verified to work with ND2725.
* Compatible
1) Seagate Momentus 7200.4 series
2) Seagate Momentus 5400.6 series
3) Hitachi Travelstar 5K series(5K520)
4) Fujitsu MHZ series (MHZ2320BH)

The compatibility problem arised by very fast USB request from EX1/EX3. This request instant response from hard drive but the instant response of those non compatible hard drive is slower.
That makes many USB NAK and result in stall of USB pipe.