Heuristic Algorithm Example

Give a counter example such that the following heuristic algorithm, for the 2-tape problem, doesn't always produce the best solution:

Algorithm:

Sort {Xi} in descending order.
Place files in tapes one at a time.
For a file being considered, assign the file to the smaller tape.

Thanks in advance.

Uni Dresden, Dusseldorf, Germany, CS206:

please also read the last lines (in red)...