I’m running new WD Red 3TB (Drive Model: WDC WD30EFRX-68EUZN0) attached to Motherboard Model: ASRock Q1900DC-ITX under Windows 7 x64 as a full ~3TB GPT partition.
Firstly, attaching this HDD, even cleaned and unformated, slows down Windows boot process significantly (system is on Intel SSD).
Secondly, after establishing a partition, when I start moving data to the drive, the first ~ 500MB are copied at normal rate and then the drive nearly stops working and the moving proces is almost halted and goes forever.
I recommend running diagnostics on this drives to make sure that the drive might be failing, you can try to use this software to test the unit for errors:
I am going to bump on this post as I have exactly the same problem.
Consistant data-transfer of about 3.3 Mb sec.
and also 1000+ hours for a diagnostic.
Extended SMART check ran without errors though.
I wasn’t able to find any software issue so I went to WD warranty service portal, I’ve registered myself and my unit, filled in a RMA (Return Material Authorization), and send my unit into nearest service center. WD has replaced my unit with new one which now operates normaly.