So are mine, and like 90% or more are from one Windows Server 2012 R2 VM, I also have WIndows 8.1 and Windows 10 VMs and those don't write much, but total writes were already reduced 15x since -beta25, like mentioned btrfs also will have some write amplification, there's a study about that, I can live with 200GB per day, just couldn't with 3TB per day.