I have two WD Caviar Black 750 Gb (SATA 3) harddrives on an Asus P8Z68-V motherboard, connected to the SATA 3 sockets. The hard drives are identical, same hardware same firmware. One is manufactured in june 2011, the other one in july.
My problem is that my hard drives perform differently on benchmark tests HD Tach and HD Tune. One of the drives performs as expected for a SATA 3 drive with avarage read of about 113 MB/s. The other one stays at 82 MB/s, a pperformance typical for SATA 2 drives. The “low-performing disk” is reported by HD Tune with avarage speed 70 MB/s, the high-performing one with avarage speed 97 MB/s. I have checked so there is no SATA 2 jumper installed on the drive. See screenshots of my results in HD Tach (there are similar results in HD Tune). Can you please help me with this and tell me what it can depend on? Is this a reason enough for RMA?