Hi all,
Since a few days I owne a MSI H77MA-G43 mainboard (Intel H77 chipset), Core I5 3450S, 2x4GB corsair memory, 4x Samsung HD204UI (2TB).
I have some problems with the RAID-5 write performances of the H77, when I create a new RAID-5 array, create 2 partitions (1 for windows, 1 for data) and install Windows server 2008 R2 (x64) on it the performance is reasonable.
When I fill the data patition (around 5.5 TB) with data the write performance decreases, the read performance remains good.

When I test each drive separate the performances are really good (same performances for all drives);
Emtpy drive:

Filled drive:

What can i do to improve the RAID-5 performance?
For your information:
- Mainboard uses latest BIOS/UEFI version
- I installed server 2008 R2 (64bit) on a 100Gigabyte partition (C:)
- I put my data on a 5.6 TB partition (D:)
- I installed the latest intel RAID drivers
- I installed intel RST tools, here are no problems visable.
- I installed the latest windows updates
Thanks.