Very bad performance Smart Array 532 with OpenServer 5.0.6

[maciej_1]

I've got raid 5 with 3x18GB (Ultra3, 10k) disks. Smart Array 532 is installed in Compaq ML350.
When I installed Linux (RH 7.3, kernel 2.4.18-3, ciss ver 2.4.30) i've got:
WRITE:
#time dd if=/dev/zero of=./test.txt bs=1024k count=1000
time 0:59 minuts:seconds
READ:
#time cat test.txt > /dev/null
time 0:10 minuts:seconds
so:
write 17,4MB/sec
read 102,4MB/sec

Unfortunately Linux was installed only for testing reason. Now I installed SCO/Caldera OpenServer 5.0.6 with 5.0.6a, using Compaq EFS 5.52 (14 Oct 2002) and:
WRITE:
#time dd if=/dev/zero of=./test.txt bs=1024k count=1000
time 5:20 minuts:seconds
READ:
#time cat test.txt > /dev/null
time 0:25 minuts:seconds
so:
write 3,2MB/sec
read 41MB/sec

Comparison:
Linux OpenServer
write 17,4MB/sec write 3,2MB/sec
read 102,4MB/sec read 41MB/sec

OpenServer write is 5 times slower than Linux, read is 2,5 times slower.
Any suggestion?

Raid 5, 3x18BG Ultra3 10k
Smart Array 532, 32kB
Firmware ML350 ROMPaq version 4.02 A (29 Jul 02) ver D11 (SP21685.exe)
Firmware Smart Array 532 ROMPaq version 3.10 A (11 Jun 02) wer 1.92 (SP19677.exe)

Thanks,
Maciej