А btrfs шустрее с файлами работает мелкими??

Да, но на Дебиане есть вот эта проблема

Dpkg and thus apt can be slow on btrfs. This is important to know if you want to use btrfs as your root filesystem and you are using stable, this is extremely annoying if your are using unstable or want to run sbuild. eatmydata helps a lot here, but a power failure can leave you with a broken dpkg database.