Also, some of the "performance problems" are simply different access models. Windows and NTFS tries to provide some database-like ACID characteristics, including transactions at the level of batches of file updates with commit/rollback support. Ext4 and Linux (intentionally) make few such guarantees and so it shouldn't be surprising have very different performance profiles, just as you might expect between a NoSQL database that makes no ACID guarantees and an SQL database with multiple types of locks and several types of transaction behaviors.