Recently I plugged a 3ware 8506-4LP RAID card into a PC, connected 
four Seagate ST3120026AS SATA disks to it and, using the card's 
built-in DOS-like configuration utility, configured them all to be in 
one RAID-5 array.

Then I plugged the card into a 164LX motherboard with a 533 MHz CPU 
and 512 MB RAM, reconnected the disks, booted from an old 1 GB SCSI 
disk which had NetBSD 2.0G on it (built from sources updated on 17 
August), and created a single 335 GB partition on the array.

The 164LX had a DE500 NIC connected too, and I discovered when 
ftp'ing to the 315 GB partition through it the trasfer rate was only 
about 270 KB/s.  ftp'ing to the old SCSI disk achieved about 3 MB/s. 
Using a 3Com 3c905C-TX instead of the DE500 gave a rate of more than 
9 MB/s to the big array.  So, I'd be happy to use the 3Com NIC except 
for the fact that I can't netboot the machine using it.

I wonder what's going on?

Here are some portions of dmesg (curiously, the lines which show the 
disk model numbers and sizes don't appear on the console during 
booting):


twe0 at pci0 dev 6 function 0: 3ware Escalade
twe0: interrupting at eb164 irq 0
twe0: 4 ports, Firmware FE8S 1.05.00.068, BIOS BE7X 1.08.00.048
twe0: Monitor ME7X 1.01.00.040, PCB Rev5    , Achip 3.20    , Pchip 1.30-66
twe0: port 0: ST3120026AS                              114473 MB
twe0: port 1: ST3120026AS                              114473 MB
twe0: port 2: ST3120026AS                              114473 MB
twe0: port 3: ST3120026AS                              114473 MB
ld0 at twe0 unit 0: 64K stripe RAID5, status: Normal
ld0: 335 GB, 43779 cyl, 255 head, 63 sec, 512 bytes/sect x 703318656 sectors

tlp0 at pci0 dev 9 function 0: DECchip 21140A Ethernet, pass 2.0
tlp0: interrupting at eb164 irq 3
tlp0: DEC DE500-AA, Ethernet address 00:00:f8:05:bb:59
nsphy0 at tlp0 phy 5: DP83840 10/100 media interface, rev. 0
nsphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto


These messages appeared in /var/log/messages when ftp'ing to the RAID array:

tlp0: transmit underrun; new threshold: 96/256 bytes
tlp0: incoming packet spilled, resetting
uid 0, pid 634, command ftp, on /usr: file system full
tlp0: transmit underrun; new threshold: 128/512 bytes


Ray