My personal reason is that zfs.ko entirely bypasses the kernel page cache, preferring its own internal cache (the ARC). Reimplementing kernel subsystems is a re

My personal reason is that zfs.ko entirely bypasses the kernel page cache, preferring its own internal cache (the ARC). Reimplementing kernel subsystems is a recipe for interoperability nightmare (c.f. the NVIDIA binary driver). For instance, this causes unnecessary memory pressure when you have a mix of ZFS and non-ZFS filesystems (e.g. SMB mounts). Additionally I curmudgeonly have yet to come to terms with the blatant layering violation of ZFS being a combined block-device-manager and filesystem. But the benefits (file-level RAID behaviour) of that are indeed clear.