USB Takes long time to unmount

[Matt Patterson]

I have noticed that if I do a lot of file transferring to a usb 2.0 
device and then immediately try to unmount the device, it takes forever. 
The device itself still thinks that it is being written to, and I assume 
it is due to caching making it appear deceivingly fast. Is there a way 
to turn off the caching on writes to external usb devices so that I can 
unmount them the instant a transfer is completed? Or is there another 
solution I am overlooking?

Matt