Ide performance (was RAID0 Performance problems)

Hi,
I've posted about performance problems with my RAID0 setup. RAID works fine, but it's too slow.
But now it seems not to be a problem with the md code, it's an ide problem. There are two HDs in my PC: /dev/hda and /dev/hdc. No other devices are attached to the ide-bus.
PC is a SMP-System, 2 Celeron 533, Gigabyte 6BXDS with Intel BX-Chipset, 66MHz FSB.
The hdparm settings:

bash-2.04# hdparm /dev/hda /dev/hdc

/dev/hda:

 multcount    =  0 (off)
 I/O support  =  3 (32-bit w/sync)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 nowerr       =  0 (off)
 readonly     =  0 (off)
 readahead    =  0 (off)

geometry = 59556/16/63, sectors = 60032448, start = 0

/dev/hdc:

 multcount    =  0 (off)
 I/O support  =  3 (32-bit w/sync)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 nowerr       =  0 (off)
 readonly     =  0 (off)
 readahead    =  0 (off)

geometry = 59556/16/63, sectors = 60032448, start = 0

I've tested a lot of variations of this settings (multcount=16, unmaskirq=0...) without succes.
The performance of the RAID doesn't increase :-(
hdparm -tT on a single HD (dev/hda3 is the RAID-partition) reports a very good performance:

bash-2.04# hdparm -tT /dev/hda3

/dev/hda3:
Timing buffer-cache reads: 128 MB in 1.42 seconds = 90.14 MB/sec
Timing buffered disk reads: 64 MB in 2.27 seconds = 28.19 MB/sec

But if I start 2 hdparms simultanous (one on /dev/hda3 the other on /dev/hdc3) the performance on the HDs decreases to 1/2 of the original speed:

bash-2.04# hdparm -tT /dev/hda3

/dev/hda3:
Timing buffer-cache reads: 128 MB in 2.27 seconds = 56.39 MB/sec
Timing buffered disk reads: 64 MB in 4.56 seconds = 14.04 MB/sec

bash-2.04# hdparm -tT /dev/hdc3

/dev/hdc3:
Timing buffer-cache reads: 128 MB in 2.25 seconds = 56.89 MB/sec
Timing buffered disk reads: 64 MB in 4.49 seconds = 14.25 MB/sec

The performance of the RAID0:

bash-2.04# hdparm -tT /dev/md0

/dev/md0:
Timing buffer-cache reads: 128 MB in 1.35 seconds = 94.81 MB/sec
Timing buffered disk reads: 64 MB in 3.11 seconds = 20.58 MB/sec

Tests with bonnie or iozone have the same reuslts, RAID is slower then a single HD :-(

Does anybody has an idea what's wrong with my setup??

Thx,
Andreas

Andreas Peter *** [email protected]