How much Time does a MergeSort take?
Only one seek is required for any single sequential access.
Only one rotational delay is required per access.
Expensive steps (i.e. involving I/O) occurring in MergeSort
During the sort phase:
- Reading all records into memory for sorting and forming runs.
- Writing sorted runs to disk
During the merge phase:
- Reading sorted runs into memory for merging.
- Writing sorted file to disk.