I did google for that information, but couldn't find any helpful resources.
If it would use multiple channels it would be nice, but I dont know and currently have no network sniffer installed.
I think only one per connection.The FTP specification says that, by default, all data transfers should be over a single connection.
FTP is a TCP based service. It is connection oriented. It needs to establish a connection between two computers through ports. FTP uses two ports. One for data and another for control. When only one port is used there will be only one channel. For more details. http://en.wikipedia.org/wiki/File_Transfer_Protocol.