How to use WD RE4 Serial ATA600 hard drives on controller that supports only SATA300?

When Serial ATA600 hard drives are plugged in a RAID controller that supports only SATA150 and SATA300, since the controller cannot understand what SATA600 is, to be defensive, it automatically default the communication ratio down to its low margin, SATA150. However, given the performance drop, now-a-day SATA600 drives are no longer backward compatible with SATA150. Although per SATA protocol, most of them can still communicate with a SATA150 controller, however, they will drop some instructions when the demands volume are higher, which causes timeout events to the raid controller. This will either greatly reduce the RAID performance by 50% or more, or worse, to cause RAID defensively offline, or worst, desolve your array and cause data lose.

Many people tried to communicated with the hard drive vendor or the RAID controller service for this issue, and they were recommended to either upgrade their controller or replace their hard drives to slower models. However, both options means high cost and many burden,

Fortunately, there is an unofficial way to overcome this difficulty.

For certain RAID controllers and hard drives, they support PHYS option, which allows you to hand set communication speed and disable the speed negotiation process.

To do this, you will need to do two things:
Raid Controller side, navigate to its controller setting menu, find the PHYS settings, and turn off the AUTO and set all PHYS ports to 3.0G.
Hard drive side, find the manual of your hard drives, find the PHYS jumper, put them on. Then put them back on the backplane.

Now boot your RAID device up, you will find that all your 6Gb/s hard drives are nolonger identified as 1.5Gb/s, but all on 3Gb/s.

In this mode, your new hard drives will happily work with your old controllers.

Have fun.