Why USB harddrive is so slow under FreeBSD?

[Dan Nelson]

In the last episode (Apr 12), Yuri said:
> I have FreeBSD-71 running with USB controller:
> uhci0: <VIA 83C572 USB controller> port 0xa800-0xa81f irq 21 at device 16.0 on pci0
> 
> I connected to it Toshiba USB hard drive HDDR500E03X:
> umass0: <Toshiba External USB HDD, class 0/0, rev 2.00/1.03, addr 2> on uhub4
> da0: <Toshiba External USB HDD 1.03> Fixed Direct Access SCSI-4 device
> 
> When I try to copy data with 'dd if=/dev/da0s1 of=/dev/null count=10000' 
> it only achieves has 0.65MB/s transfer speed.
>
> What's wrong, why is it so slow?

Increase your blocksize.  dd's default is 512 bytes.  Try bs=64k

-- 
	Dan Nelson
	dnelson at allantgroup.com