diff --git a/etc/emqx.conf b/etc/emqx.conf
index 1564ed73d..0c4ea81a5 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -211,7 +211,7 @@ node.data_dir = {{ platform_data_dir }}
 ## Value: 0-1024
 ##
 ## vm.args: +A Number
-node.async_threads = 32
+## node.async_threads = 4
 
 ## Sets the maximum number of simultaneously existing processes for this
 ## system if a Number is passed as value.
diff --git a/etc/vm.args b/etc/vm.args
index 43e6467d9..a32619be1 100644
--- a/etc/vm.args
+++ b/etc/vm.args
@@ -1,6 +1,6 @@
-##############################
-# Erlang VM Args
-##############################
+######################################################################
+## Erlang VM Args
+######################################################################
 
 ## NOTE:
 ##
@@ -52,7 +52,8 @@
 +spp true
 
 ## Sets the number of threads in async thread pool. Valid range is 0-1024.
-#+A 8
+## Increase the parameter if there are many simultaneous file I/O operations.
++A 4
 
 ## Sets the default heap size of processes to the size Size.
 #+hms 233
@@ -92,4 +93,8 @@
 #+sct L0-3c0-3p0N0:L4-7c0-3p1N1
 
 ## Sets the mapping of warning messages for error_logger
-#+W w
\ No newline at end of file
+#+W w
+
+## Specifies how long time (in milliseconds) to spend shutting down the system.
+## See: http://erlang.org/doc/man/erl.html
+#-shutdown_time 15000
diff --git a/priv/emqx.schema b/priv/emqx.schema
index 642da69a2..a6966f0a5 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -235,7 +235,6 @@ end}.
 
 %% @doc More information at: http://erlang.org/doc/man/erl.html
 {mapping, "node.async_threads", "vm_args.+A", [
-  {default, 64},
   {datatype, integer},
   {validators, ["range:0-1024"]}
 ]}.