NetBSD continues using the FFS file-system by default while it’s offered ZFS support that has been slowly improving — in NetBSD-CURRENT is the ability to use ZFS as the root file-system if first booting to FFS, for example. There may be another modern file-system option soon with an effort underway to port DragonFlyBSD’s HAMMER2 over to NetBSD…

Source: Phoronix – DragonFlyBSD’s HAMMER2 File-System Being Ported To NetBSD