Only put VM disk metadata into the ARC.

The guest VMs should have their own filesystem cache so I see no need to pollute the host's cache.

ansible/roles/bhyve/files/bhyve_netgraph_bridge.bash

@@ -68,7 +68,7 @@ IP_RANGE="$IP_RANGE"
 BRIDGE_NAME="$BRIDGE_NAME"
 INTERFACE_NAME="$INTERFACE_NAME"
 EOF
-    zfs create -s "-V${gigabytes}G" -o volmode=dev "$zfs_path/disk0"
+    zfs create -s "-V${gigabytes}G" -o volmode=dev -o primarycache=metadata -o secondarycache=none "$zfs_path/disk0"
 }
 
 function start_vm {