Have a WD MyBook 3TB USB external hard drive containing a WD30EZRX. Also have a WD easyStore 8TB USN hard drive containing a WD 80EFAX. Both are running off an AsRock Z170M (All USB ports are v3.0) motherboard which is also running two internal HDDs and two internal SSDs which all are in SATA III mode.
CrystalDiskInfo reports that both USB drives are capable of SATA III (6Gb) but the WD MyBook 3TB is only running in SATA II mode.
I suspect that I found the answer. Not being an expert on such matters I tried to make sense of this and the details below seem to be the most logical. Looking at a review of the 6TB from the same model range I found this:
‘The Western Digital MyBook 6Tb external drive is based around a Western Digital 6Tb Green drive, placed inside an enclosure sporting a SATA II to USB 3.0 chipset.’
From what little I know we seem to have a USB chipset in these MyBooks that limits the SATA III’s 6Gbit/s hard drive (WD30EZRX) to SATA II’s 3Gbit/s. USB3.0 can potentially transfer data at up to 5Gbit/s speeds. Therefore the hard drive’s potential is being throttled quite a lot. That is sad considering the MyBook was specified by WD as a USB 3.0 item.
