Hi,

Recently I have noticed a issue after upgrading from 4.0.14 to 4.0.20

When using Mongo version 4.0.14, I have added 1 shard on top of existing 2 shards. turnedOn the balancer and chunks migrated to newly added shard (3rd) and I could see dataSize reduced on older shards, by using "compact" I reclaimed storageSize after migration.

After upgrading to 4.0.20, I have added 1 more shard on top of 3 shards, turnedOn the balancer and chunks migrated to newly added shard (4th) and I did not notice dataSize reduced on older shards, I also verified by looking at "file bytes available for reuse" on db.stats() and db.coll.stats()