I wrote to Asus with this issue and they got back to me with this "sir ,i also have tested like that . the result is similiar . Promise dc20378 has 2 sata ports and 1 IDE ports , the ide port can connect 2 IDE harddisk , you can use the 2 disks in raid0 or raid 1 mode ,but , due to the 2 disks are in same IDE channel , the disk ! performance will be very poor ,even a bit lower than single harddisk . if you use a sata harddisk to replace one ide disk, then use sata+pata disk as raid0 ,the disk performance is very high , almost double the single disk score . and you also know that ,the Seagate U5/U6 disk are all low cost low speed disk , so your disk performance is bad . i contacted the Promise before , they told my they don't recommend to build RAID0 on that only IDE port too" I guess I will try some other faster drives and see if it does the same. If not I will go for SATA drive as it has 2 seperate channels. By the way thank you very much for all your help ironfist241. Cheers shsurury