WD20EARS in a USB3.0 External Enclosure (Sustained write 22MB/sec)

I have just installed a WD20EARS 2Tb drive into a rosewill RX358 USB 3.0 External Enclosure.

I formatted the drive first internally hooked directly to a SATA port in my computer, then placed it into the enclosure and had no problems having the computer recognize it and write and read.

However, when I run HDTune and do a file read / write benchmark test…I am maxing out at about 22MB/sec.  This seems really slow.  When I had one of these in my computer hooked up directly via SATA, I got much higher…around 55MB/sec.

Anyone have an idea what is going on here.

I am very tech savvy, so any suggestions would be appreciated and I can follow along with just about any instructions…


As a quick guess, it sounds like it’s only connecting as USB2.0

The 22MB/sec is about the going rate for my USB2 externals.  The burst rate is only 60, and I rarely have sustained speeds above 30 – they’re usually in the 20-30 MB/s range.

Although, the 55 through SATA sounds a little suspect to me too… I usually get speeds in the 90-100 range from my SATA Caviar drives.

Actually, if I rememer correctly from other posts, it could be your PC’s power settings.  I believe people who have had WD USB3 drives that only work as USB2, have had success in changing their power settings.  It seems that USB2 and USB3 have different power requirements, and if the enclosure gets the wrong power, it falls back to USB2.

The following document specifies a maximum sustained data transfer rate of 110MB/s (via SATA).

WD Caviar Green Series Disti Spec Sheet: