I've been running some tests since i got my new WD20EARS drive and i found that when compared to my RAID 0 setup with 2 WD2500KS, the speeds are very much alike...
I've formatted my pc and ran the tests in HDTune and HDTach here are the results:
My guess it's the AMD drivers problem because when I was installing Windows 7, I tried to use the 64-bit drivers and it would say that they were not signed so i chose the 32-bit and it let me go on with the installation...
Green drives sacrifice performance for energy savings. The caviar black are WD's performance edition drives while the blue's are their mainstream drives.
Other than that, you don't list your specs or which RAID controller you have the drives hooked into as most motherboards that have RAID have two controllers.
Yes I know that green is not the best performer, but my problem here is the comparison between the two, I think that the RAID 0 should be running at better speeds that this...
I'm using the AMD controller, the options I chose during the RAID setup were
Stripe block: 128Kb
fast init: off (checked on a few web sites and most of them said this would be better because it would write zeroes on the drive instead of writing over the old data)
gigabyte boundary: off
And the alst option which I dont remember the name i know it was WritheThru and wouldn't let me change it...
I'm using 2 WD2500KS in this array maybe it's the 16mb cache?
Hmm, do you have AMD RAID eXpert installed? You can control some settings through there, like enabling NCQ (which is off be default). Even so it shouldn't make that much of a difference. I have a 3 drive RAID 0 and I get 3-4 times that performance (intel controller 640Gb 7200RPM drives).
I know some controllers can give odd performance. Have you tried these on a different controller or even different SATA ports?
Edit: Cache wont make that buch of a difference.
Edit: looking at HD tach it looks like you drives are running in SATA 1 mode you never go above 150MB/s. Are you using SATA 2 or 3 cables? Is there a jumper on the drive that is forcing SATA 1 mode?
3x 6400AAKS in RAID 0 (drive is currently busy with reads and writes (128KB stripe) (ignore the really hugh burst on this one I have caching on)
And 2x 5400 RPM 500GB 2.5' drives in a RAID 1
My 2.5 disks burst speed wise come within spitting range of your 3.5" 2TB, IMO something is wrong.
If you compare the difference betwen your first two charts, you see the second chart with the single drive has a good curve to it, while the RAID 0 first chart stays level in the beginning then drops off which usually mean you have saturated the interface, mechanical drives should have a nice downward curve. It might also be drivers.