WD reply to my request by that :
This being said, as mentioned the noise you hear every 5 seconds is by design to prevent media lube build up due to prolonged dwelling at a single location.
Please keep in mind that the noise heard should not affect the performance that we have listed in our specification sheet for this model drive. I understand this is your first drive where you have noticed this, but again I can assure you based on the information provided, this appears to be operation as designed.
Performance impact during sequential read (whole disk) and random read access (launched on both drive at the same time)
Write speed : WD4001 141Mo/s – WD4005 179Mo/s
Latency (random read) : WD4001 max 2sec – WD4005 max 6.11sec (!)
Request completed (random read) : WD4001 101replies – WD4005 65replies (!)
WD4005 is a lot more noisy during same operations than the older WD4001 and 3x higher latency for 2x less replies.
Yes this 5sec noise isn’t normal at all and impact a lot the performance. This noise occur even during sequential and read random access but media lube is done by disk activity without need the firmware help !
Now can you reprogram your firmware and correct these bugs and performance issues ?