USB 2.0 speed

[chengbin]

I have had 2 external hard drives. Both of them doesn't go faster than around 30mb/s. Is this USB 2.0's limitation? I thought the theoretical speed is 60mb/s (I know it is theoretical, but half as much?) Is this normal?

What kind of speed should a modern hard drive hit?

 

[wuzy]

It's a USB<->SATA/PATA controller limitation. 30MB/s is quite good.
My cheapo PATA 2.5" USB2.0 enclosure can only attain ~21MB/s.