RAID0 performance odditity

[Michael Trainor]

I've got a Dual Celeron 466 system (Abit BP6) running four maxtor IDE hard drives on the ATA66 controller (using ATA33 for all four drives).  Two of the drives are 27GB 7200RPM, one is 17GB 5400RPM and the fourth is 13GB 5400RPM.  The two smaller drives are about 9.5MB/sec with hdparm -t and the two larger drives are about 20MB/sec with hdparm.   The array is 78GB and currently I've got a chunk size of 32 (though I've played with other sizes from 8 to 64).   Running the array I get about 20.25MB/sec with hdparm.   In the old days (using the raid software, circa 2.0.36) I used to get about 28-30MB/sec with the 13, 17 and a 8GB drive.  I can run hdparm -t /dev/hde & hdparm -t /dev/hdg and get a combined 37MB/sec or so by adding the numbers together.   Does anyone have any idea why the performance is so low?  I'd expect numbers at least in the 40MB/sec range, being that the drives are on seperate channels on the ide.   I'm running 2.2.14pre11 with the ide patch and the latest raid patch (8/24?).  ATA/66 mode is disabled for the channels (lock up problems).  I also got similar numbers on a seperate motherboard running the stock 2.2.13 with the raid patches.