about usb2

[Henri Girard]

Hi,
I have an archos (audio video mp4 reader) on usb2, usb2 are connected to 
belkin pci card. I tried the connection on few flavours of linux, 
finally i choosed dapper. Each time i open my archos i have two mounts :
sda and sda1, but sda had nothing always empty and sda1 has the 
arborescence. If i closed usb2 sda sda1 closed too ?
Is this normal behavior ?
if anyone has an explanation, greatly appreciated I would like to get 
rid of sda :)
regards
Henri