This article gives some recommendations for configuration options to tune a migration. Proper analysis should be performed, but these general guidelines may help.
Set folder splitting to 100,000 items. (Inserting new data into folders with many items gets progressively slower)
Set PST Rollover Threshold (MiB) in Archive Shuttle Links page to 1 Gb.
Ensure that setting ‘Finalize finished PSTs in Stage 1‘ is enabled in Native Import Module settings page.
Ensure that Item Parallelism is kept low (1-2 is ideal). File parallelism can be higher (e.g. 10)