Version:           4:4.3.4-0ubuntu1~karmic1 (using KDE 4.3.4)
OS:                Linux
Installed from:    Ubuntu Packages

When I drag-and-drop files from my hard disk to a USB drive or vice-versa, unless I drag them all over at once or wait for the first to finish before dragging the second, Dolphin tries to multitask the copy operations. This slows down the transfer tremendously.

To reproduce: Plug in a USB flash drive, USB external hard drive, or internal hard drive with USB adapter. Click the Device Notifier, then click the newly plugged-in drive. In another Dolphin window, drag-and-drop a large file or group of files from the hard drive to the USB drive or vice-versa, then drag-and-drop another while the first is still copying or moving.

Expected behaviour: Dolphin detects (or delegates the file operation to another program which detects) that the source or destination path is a disk already running at maximum throughput. The second copy or move operation enters a queue, and it starts only when it can do so without delaying an operation already in progress.