USB 2.0 vs FireWire?

[Chris Ruprecht]

Hello,

I have a Dell PowerEdge 2500 server with FC6 + latest updates installed.

For backup, I want to use 2 external disk drives, 300 GB each (all 
internal stuff is SCSI). I bought a USB 2.0/FireWire combo card and am 
running a few tests and to my great surprise, USB 2 (480 mbps) is way 
faster than FireWire 400 (400 mbps). I get this from hdparm:

Connected as USB 2.0 drive:
hdparm -t -T /dev/sdd

/dev/sdd:
 Timing cached reads:   948 MB in  2.00 seconds = 473.56 MB/sec
 Timing buffered disk reads:   76 MB in  3.03 seconds =  25.11 MB/sec

Connected as FireWire 400 drive:
hdparm -t -T /dev/sdd

/dev/sdd:
 Timing cached reads:   948 MB in  2.00 seconds = 473.05 MB/sec
 Timing buffered disk reads:   32 MB in  3.07 seconds =  10.44 MB/sec

To make sure that hdparm is not messing with me, as the only reference I 
find in its man page is relating to IDE and SCSI drives, I tested some 
simple copy command of a 4 GB file. I did each command twice in a row, 
to avoind any skewing of the results by anything in OS buffers.

USB 2.0 Mode:
time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx3
`/home/db/pm/pm_10.d2' -> `/media/extd/xxx3'

real    3m20.819s
user    0m0.988s
sys     0m54.483s
[root at mars ~]# time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx4
`/home/db/pm/pm_10.d2' -> `/media/extd/xxx4'

real    3m18.799s
user    0m1.048s
sys     0m54.791s

FireWire Mode:
time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx1
`/home/db/pm/pm_10.d2' -> `/media/extd/xxx1'

real    7m33.109s
user    0m1.196s
sys     0m52.439s
[root at mars ~]# time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx2
`/home/db/pm/pm_10.d2' -> `/media/extd/xxx2'

real    9m13.851s
user    0m1.108s
sys     0m55.191s


I used the same drive, a Maxtor 320 GB drive that was on sale recently, 
which is mounted inside an Adaptec external USB/FireWire combo case.

Any ideas why FireWire is so much slower than USB? Should I look at the 
card, the drive or the drivers? I would really like to use the FireWire 
side of things, but not at this ridiculous  speed.

Thanks for any pointers.
Chris