Promise SX8 driver performance

[Matt <matt@signalz.com>]

Hello all. I've got a Promise SX8 SATA controller and the performance
seems a little off. I'm using a debian-built 2.6.9 kernel and the
read/write I/O seems to level off around 80-90 MB/s. When I use the same
hardware in Windows, sequential I/O goes up to 218 MB/s. (That's about
the limit of my motherboard's buses.) If I move some disks to the
on-board SATA controller, I can get the I/O to go higher but never as
high as in Windows.

Is this a problem with my expectations, my testing, or the driver? 


Some Bonnie numbers for a raid 0 array of Seagate 7200.7's (2 GB file,
sequential, MB/s):

Disks/cntl        Write    Read
-----             -----    ----
1 (sx8)              57      63
2 (sx8)              69      75
2 (ESB)             111     121
3 (sx8)              75      79
3 (1 sx8, 2 ESB)    141     125
4 (sx8)              89      80
4 (2 sx8, 2 ESB)    135     150
5 (sx8)              88      79
6 (sx8)              91      75

Some numbers from Sandra (ugh) in W2K Pro with the latest Promise
drivers and using software RAID 0 (sequential, MB/s):

Disks/cntl      Write    Read
-----           -----    ----
1 (sx8)            56      62
2 (sx8)           106     122
3 (sx8)           151     176
4 (sx8)           178     209
5 (sx8)           180     218
6 (sx8)           179     218
6 (4 sx8, 2 ESB)  169     207


My full hardware:

Supermicro P4SCi motherboard (7210 chipset, 6300ESB SATA on-board)
3.0 GHz P4 Northwood w/ HT enabled
(2) 512MB DDR400 dual channel (non-ECC)
Promise SX8 SATA controller
(6) 200 GB Seagate 7200.7
(1) 40 GB Seagate Baraccuda IV (boot)
Adaptec 2940U