diff --git a/plugins/solaris/io_disk b/plugins/solaris/io_disk
index ee2c11d8..3e222d48 100755
--- a/plugins/solaris/io_disk
+++ b/plugins/solaris/io_disk
@@ -9,10 +9,11 @@
   These functions are implemented:
      ops     : similar to iostat r/s, w/s
      bytes   : similar to iostat kr/s, kw/s 
-     busy    : similar to iostat %b, %w
+     busy    : similar to iostat %b, %w (%w usually indicates 0 in Sol10,11)
      queue   : similar to iostat actv, wait
      latency : similar to iostat asvc_t, wsvc_t
 
+  This plugin is improved from Solaris io_busy_, io_ops_, io_bytes_ plugins.
   Any device found in /usr/bin/kstat can be monitored.
 
   Tested with Solaris 10 and 11, and it should work with Solaris 8, 9.
@@ -30,19 +31,26 @@
   By default, this plugin monitors disk devices. And also it can monitor 
   NFS and Tape devices as much as io_* plugins with setting environments.
 
+  Note that instance names of nfs (e.g. nfs1) can be changed after reboot or
+  remount, this plugin may not monitor nfs properly. (same as original ones)
+
 =head1 ENVIRONMENT VARIABLES
 
   env.class - kstat class. See man kstat -c option.
     example:  env.class  /disk|nfs|tape/
     default:  disk
 
-  env.module - Module name. Only used in internal graph name.  If you would not
-    to like to take over RRDs generated by io_*_sd plugins, please change it 
-    to another name.
-
+  env.module - Module name. Only used in internal graph name.  
     example:  env.module  something
     default:  sd
 
+    If you would not like to take over RRDs generated by io_*_sd plugins,
+    please change it to another name.
+
+    And also, if you would like to take over RRDs of nfs, tape devices,
+    please set it 'nfs' or 'tape' (and set env.class, env.module_regex).
+    It may be good to link like ln -s /path/to/io_disk io_nfs if necessary.
+
   env.module_regex - kstat module. See man kstat -m option.
     example:  env.module_regex  /^(s?sd|vdc|zvblk|dad|md|nfs|tape)$/
     default:  /^(s?sd|vdc|zvblk|dad|md)$/
@@ -187,16 +195,15 @@ do_config() {
         echo "graph_width $graph_width"
     fi
 
+    # Get device instance names by kstat
     kstat -p -c "$class" -m "$module_regex" -s "/^${conf_in}\$/" | sed 's/:/ /g' | awk '{ print $3 }' | \
     while read -r dev
     do
-        if is_excluded "$dev" ; then
-            continue
-        fi
+        is_excluded "$dev" && continue
 
-        # replace instance name to logical device name if exists
+        # Replace instance name to logical device name if exists
         ref="name_$dev"
-        devname=${!ref:-}
+        devname=${!ref:-}  # ${!varname} means indirect evaluation (similar to eval)
 
         # reads and writes are necessary to calculate latency
         if [ "$func" = 'latency' ]; then
@@ -244,12 +251,18 @@ do_getvalue() {
 
     echo "multigraph ${plugin_name}_${func}_${module}"
 
+    # Get device instance names, stat names and values by kstat
+
+    # kstat output example:
+    #   $ kstat -p -c disk -m '/^sd$/' -s '/^reads$/'
+    #   sd:0:sd0:reads  51432610
+    #   sd:1:sd1:reads  52671435
+    #   ...
+
     kstat -p -c "$class" -m "$module_regex" -s "$stat_regex" | sed 's/:/ /g' | awk '{ print $3,$4,$5 }' | \
     while read -r dev stat value
     do
-        if is_excluded "$dev" ; then
-            continue
-        fi
+        is_excluded "$dev" && continue
 
         echo "${dev}_${stat}.value ${value%.*}"
     done
@@ -285,7 +298,7 @@ getvalue() {
     done
 }
 
-# main
+# Main
 case ${1:-} in
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