[RE] Poorer performance with Raid0 then without?

Here is more hdparm data. It looks like bad news.

Note: for whatever reason, /dev/md0 does not seem to be my RAID device. I
set up my raid (via trial and error) with dmraid, and it gave me
/dev/mapper/sil_agbgdgbjfhei. I have always felt there was something
not-right about  that.
Second, the errors hdparm reports from -tT look significant.
Finally, "Timing cached reads" are much lower then single drives. I don't
know what this really means in a RAID context. 

I tried removing the third drive on the board (primary slave), no effect. 

Anyway, given the errors, is this a RAID software problem, or a piece of
junk RAID adapter card?

Thanks so much, folks.

Listbox
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/dev/hde:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 19457/255/63, sectors = 312581808, start = 0

/dev/hdg:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 19457/255/63, sectors = 312581808, start = 0

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hprarm -tT /dev/md0
read() hit EOF - device too small

/dev/md0:
 Timing buffered disk reads:  read() hit EOF - device too small
BLKFLSBUF failed: No such device
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: No such device

hprarm -tT /dev/mapper/sil_agbgdgbjfhei
/dev/mapper/sil_agbgdgbjfhei:
 Timing cached reads:   HDIO_DRIVE_CMD(null) (wait for flush complete)
failed: Inappropriate ioctl for device
1288 MB in  2.00 seconds = 643.22 MB/sec
 Timing buffered disk reads:  HDIO_DRIVE_CMD(null) (wait for flush complete)
failed: Inappropriate ioctl for device
284 MB in  3.01 seconds =  94.27 MB/sec
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dev/hda:
Timing cached reads:   1668 MB in  2.00 seconds = 834.10 MB/sec
Timing buffered disk reads:   88 MB in  3.05 seconds =  28.87 MB/sec

/dev/hdb:
Timing buffered disk reads:  
/dev/hdc:
Timing cached reads:   1696 MB in  2.00 seconds = 847.36 MB/sec
Timing buffered disk reads:   88 MB in  3.05 seconds =  28.82 MB/sec

/dev/hde:
Timing cached reads:   1680 MB in  2.00 seconds = 838.49 MB/sec
Timing buffered disk reads:  168 MB in  3.03 seconds =  55.46 MB/sec

/dev/hdf:
Timing cached reads:   1688 MB in  2.00 seconds = 843.57 MB/sec
Timing buffered disk reads:  164 MB in  3.00 seconds =  54.59 MB/sec

/dev/hdg:
Timing cached reads:   1696 MB in  2.00 seconds = 846.68 MB/sec
Timing buffered disk reads:  162 MB in  3.03 seconds =  53.45 MB/sec