MergeSort: Advantages
It can be applied to files of any size.
Reading of the input during the run-creation step is sequential ==> Not much seeking.
Reading through each run during merging and writing the sorted record is also sequential. The only seeking necessary is as we switch from run to run.
If heapsort is used for the in-memory part of the merge, its operation can be overlapped with I/O
Since I/O is largely sequential, tapes can be used.