So, I just had another of these panics: panic: kmem_alloc(131072): kmem_map too small: 400011264 total allocated what I did to provoke it: zfs rollback room/freebsd at presnap From loader.conf: vm.kmem_size=536870912 vm.kmem_size_max=536870912 vfs.zfs.arc_max=409715200 vfs.zfs.prefetch_disable="1" Darren