I implemented the same thing in Production and reassignment is showing as completed. But old segmented logs and future folder is not getting deleted.
From the logs i can see as below
INFO [ReplicaAlterLogDirsThread-1]: Partition XXXX-1 has an older epoch (102) than the current leader. Will await the new LeaderAndIsr state before resuming fetching. (kafka.server.ReplicaAlterLogDirsThread) INFO [Partition XXX-1 broker=3] XXX-1 starts at Leader Epoch 106 from offset 0. Previous Leader Epoch was: 105 (kafka.cluster.Partition)
After restarting the service, it tried to copy the data from one folder to other folder for some time and then stopped