Disk Performance Issues

[Josh Paetzel]

I've got a FreeBSD 4.8-STABLE system with a Maxtor 6L040J2 ATA/133 7200 RPM 
IDE OS drive in it on a gigabtye GA-7VRXP motherboard.  I've also got a pair 
of Western Digital WD800BB 7200 RPM ATA/100 drives in RAID 1 on an onboard 
Promise 20276 ATA/133 RAID Controller.  

atacontrol reports that all the drives are being properly probed:

===root at markx ('tty') /storage/os_isos -> atacontrol mode 0
Master = UDMA133 
Slave  = ???
===root at markx ('tty') /storage/os_isos -> atacontrol mode 1
Master = PIO4 
Slave  = PIO4
===root at markx ('tty') /storage/os_isos -> atacontrol mode 2
Master = UDMA100 
Slave  = ???
===root at markx ('tty') /storage/os_isos -> atacontrol mode 3
Master = UDMA100 
Slave  = ???


My issue is that I'm seeing sustained transfer rates on 600-700 meg files in 
the 5-6 Meg/second range...about 1/4 of what the drives are capable of.  Does 
anyone have any advice on where to go from here in troubleshooting this issue?

TIA, 

Josh