Comment by ryao

You have a couple options:

1. Delete the snapshots and rewrite the files in place like how people do when they want to rebalance a pool.

2. Use send/receive inside the pool.

Either one will make the data use the new layout. They both carry the caveat that reflinks will not survive the operation, such that if you used reflinks to deduplicate storage, you will find the deduplication effect is gone afterward.