RAID5 performance - hows this doing?

[VtLgsr245]

I just ran HD-tach out of interest on my array and it produced the following graph - is this normal? Any comments?

System: Q6600, Server2003, Areca 1231, 11*Seagate 1TB drives

 

[houkouonchi]

Why does it say 8TB if its 11 drives in raid5? should be 10 TB. Anyway that is not normal at all (assuming you have nothing access the array). Here is what I got on an ARC-1231 with 12x1TB seagate drives also in raid5:

Also I would suggest doing the long test not the short one. I also assume the array is in a normal status right? If it was rebuilding or initializing I could maybe see numbers like that but even then those numbers are lower than what I would expect.