testing raid 0

[<alx2001_(_at_)_medimex_(_dot_)_ro>]

Hi, 
I've succesfully configured raid 0 using raidctl on tow hdd (non SCSI; wd)
So I went to the next step of testing but I'm disappointed in the
improvement. Actually it's not an improvement is a loss, I think. Take a
look below:

bash-2.05# mount
/dev/raid0c on /mnt type ffs (local)

bash-2.05# pwd
/mnt
bash-2.05# dd if=/dev/zero of=a.file bs=10m count=15
15+0 records in
15+0 records out
157286400 bytes transferred in 20 secs (7864320 bytes/sec)
bash-2.05# pwd
/
bash-2.05# dd if=/dev/zero of=a.file bs=10m count=15
15+0 records in
15+0 records out
157286400 bytes transferred in 9 secs (17476266 bytes/sec)
bash-2.05# 

Hmmm is this a raid ??? or what is it?

Another thing, check this out:
bash-2.05# iostat 1
      tty            cd0             wd0             wd1           raid0
cpu
 tin tout  KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s
us ni sy in id
   1  134  0.00   0 0.00  18.03  12 0.22  15.41   9 0.14  15.25  18 0.27
1  0  1  0 98
  13  268  0.00   0 0.00  29.38 128 3.67  31.18 116 3.53  30.24 244 7.21
1  0 16  0 83
  13   89  0.00   0 0.00  27.16 162 4.31  31.23 144 4.38  29.07 306 8.69
0  0

and :

bash-2.05# iostat 1
      tty            cd0             wd0             wd1           raid0
cpu
 tin tout  KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s
us ni sy in id
   3   91  0.00   0 0.00  62.54 177 10.82   0.00   0 0.00   0.00   0 0.00
2  0 39  6 53
   0   90  0.00   0 0.00  62.72 271 16.59   0.00   0 0.00   0.00   0 0.00
6  0 41  0 53
   0   90  0.00   0 0.00  62.73 273 16.72   0.00   0 0.00   0.00   0 0.00
1  0 31  3 65
   1   90  0.00   0 0.00  62.06 269 16.29   0.00   0 0.00   0.00   0 0.00
0  0 38  3 58
....

My raid.conf looks like:
START array
1 2 0

START disks
/dev/wd0i
/dev/wd1j

START layout
32 1 1 0

START queue
fifo 100 

What can I make to work around this problem. I have openbsd29 current.
Tks