Slow Raid 5 write speeds on P6T deluxe

Hi guys,

I recently set up a raid 5 using the on board raid controller for the P6T deluxe.
I'm using 4 SATA 2 Western Digital 1TB green drives.

When benchmarking using ATTO I can see a big roll off of write speed after 1024.

The raid is working, and read speeds are good. Write seems terrible though. I'm using Windows 7 64.
I've also noticed that the "RAID controller" has no driver installed in device manager, and seems unable to find one. I tried reinstalling the latest drivers from ASUS and still no joy.

Does anyone have any idea what could be causing this, or how to fix it?
Any help would be greatly appreciated!
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More about slow raid write speeds deluxe
  1. If you already installed Intel Rapid Storage Technology, then the drivers are installed and the RAID can be monitored from Windows:

    It's normal for RAID 5 writes to be slow when using the ICH10R. If you need write performance, then a caching controller with a battery backup unit (BBU) is required. Another solution is switch to RAID 10.
  2. As GhislainG pointed out, slow writes for RAID5 using the ICH10R are normal. The parity calculations for RAID5 add a level of overhead that is not needed for RAID0 or RAID1. That is why it is frequently recommended that you use a an add-in RAID controller card for RAID5, which which will do the parity calculations in specialized hardware on the card without using CPU resources.

    Contributing to slow writes is the fact that the Green drives have lower rotational speed (about 5400 RPM) vs the more standard rate of 7200RPM. The slow speed is what makes the drive quieter and more energy efficient.
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