diff --git a/lib/fluent/plugin/storage_local.rb b/lib/fluent/plugin/storage_local.rb
index a431453f9b..326a162152 100644
--- a/lib/fluent/plugin/storage_local.rb
+++ b/lib/fluent/plugin/storage_local.rb
@@ -29,10 +29,16 @@ class LocalStorage < Storage
       DEFAULT_FILE_MODE = 0644
 
       config_param :path, :string, default: nil
-      config_param :mode, :integer, default: DEFAULT_FILE_MODE
-      config_param :dir_mode, :integer, default: DEFAULT_DIR_MODE
+      config_param :mode, default: DEFAULT_FILE_MODE do |v|
+        v.to_i(8)
+      end
+      config_param :dir_mode, default: DEFAULT_DIR_MODE do |v|
+        v.to_i(8)
+      end
       config_param :pretty_print, :bool, default: false
 
+      attr_reader :store # for test
+
       def initialize
         super
         @store = {}
@@ -42,9 +48,13 @@ def configure(conf)
         super
 
         @on_memory = false
-        if !@path && !@_plugin_id_configured
+        if @path
+          # use it
+        elsif root_dir = owner.plugin_root_dir
+          @path = File.join(root_dir, 'storage.json')
+        else
           if @persistent
-            raise Fluent::ConfigError, "Plugin @id or path for <storage> required to save data"
+            raise Fluent::ConfigError, "Plugin @id or path for <storage> required when 'persistent' is true"
           else
             if @autosave
               log.warn "both of Plugin @id and path for <storage> are not specified. Using on-memory store."
@@ -53,18 +63,11 @@ def configure(conf)
             end
             @on_memory = true
           end
-        elsif @path
-          # ok
-        else # @_plugin_id_configured is true
-          log.warn "path for <storage> is not specified. Using on-memory store temporarily, but will use file store after support global storage path"
-          @on_memory = true
-          ## TODO: get process-wide directory for plugin storage, and generate path for this plugin storage instance
-          # path = 
         end
 
         if !@on_memory
           dir = File.dirname(@path)
-          FileUtils.mkdir_p(dir, mode: @dir_mode) unless File.exist?(dir)
+          FileUtils.mkdir_p(dir, mode: @dir_mode) unless Dir.exist?(dir)
           if File.exist?(@path)
             raise Fluent::ConfigError, "Plugin storage path '#{@path}' is not readable/writable" unless File.readable?(@path) && File.writable?(@path)
             begin
@@ -75,7 +78,7 @@ def configure(conf)
               raise Fluent::ConfigError, "Unexpected error: failed to read data from plugin storage file: '#{@path}'"
             end
           else
-            raise Fluent::ConfigError, "Directory is not writable for plugin storage file '#{dir}'" unless File.writable?(dir)
+            raise Fluent::ConfigError, "Directory is not writable for plugin storage file '#{@path}'" unless File.stat(dir).writable?
           end
         end
       end
diff --git a/test/plugin/test_storage_local.rb b/test/plugin/test_storage_local.rb
index f125234347..9cf8df41f0 100644
--- a/test/plugin/test_storage_local.rb
+++ b/test/plugin/test_storage_local.rb
@@ -1,8 +1,294 @@
 require_relative '../helper'
 require 'fluent/plugin/storage_local'
+require 'fluent/plugin/input'
+require 'fluent/system_config'
+require 'fileutils'
 
 class LocalStorageTest < Test::Unit::TestCase
-  test 'syntax' do
-    assert true
+  TMP_DIR = File.expand_path(File.dirname(__FILE__) + "/tmp/storage_local#{ENV['TEST_ENV_NUMBER']}")
+
+  class MyInput < Fluent::Plugin::Input
+    helpers :storage
+    config_section :storage do
+      config_set_default :@type, 'local'
+    end
+  end
+
+  setup do
+    FileUtils.rm_rf(TMP_DIR)
+    FileUtils.mkdir_p(TMP_DIR)
+    Fluent::Test.setup
+    @d = MyInput.new
+  end
+
+  teardown do
+    @d.stop unless @d.stopped?
+    @d.before_shutdown unless @d.before_shutdown?
+    @d.shutdown unless @d.shutdown?
+    @d.after_shutdown unless @d.after_shutdown?
+    @d.close unless @d.closed?
+    @d.terminate unless @d.terminated?
+  end
+
+  sub_test_case 'without any configuration' do
+    test 'works as on-memory storage' do
+      conf = config_element()
+
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_nil @p.path
+      assert @p.store.empty?
+
+      assert_nil @p.get('key1')
+      assert_equal 'EMPTY', @p.fetch('key1', 'EMPTY')
+
+      @p.put('key1', '1')
+      assert_equal '1', @p.get('key1')
+
+      @p.update('key1') do |v|
+        (v.to_i * 2).to_s
+      end
+      assert_equal '2', @p.get('key1')
+
+      @p.save # on-memory storage does nothing...
+
+      @d.stop; @d.before_shutdown; @d.shutdown; @d.after_shutdown; @d.close; @d.terminate
+
+      # re-create to reload storage contents
+      @d = MyInput.new
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert @p.store.empty?
+    end
+
+    test 'warns about on-memory storage if autosave is true' do
+      @d.configure(config_element())
+      @d.start
+      @p = @d.storage_create()
+
+      logs = @d.log.out.logs
+      assert{ logs.any?{|log| log.include?("[warn]: both of Plugin @id and path for <storage> are not specified. Using on-memory store.") } }
+    end
+
+    test 'show info log about on-memory storage if autosave is false' do
+      @d.configure(config_element('ROOT', '', {}, [config_element('storage', '', {'autosave' => 'false'})]))
+      @d.start
+      @p = @d.storage_create()
+
+      logs = @d.log.out.logs
+      assert{ logs.any?{|log| log.include?("[info]: both of Plugin @id and path for <storage> are not specified. Using on-memory store.") } }
+    end
+  end
+
+  sub_test_case 'configured with path' do
+    test 'works as storage which stores data on disk' do
+      storage_path = File.join(TMP_DIR, 'my_store.json')
+      conf = config_element('ROOT', '', {}, [config_element('storage', '', {'path' => storage_path})])
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal storage_path, @p.path
+      assert @p.store.empty?
+
+      assert_nil @p.get('key1')
+      assert_equal 'EMPTY', @p.fetch('key1', 'EMPTY')
+
+      @p.put('key1', '1')
+      assert_equal '1', @p.get('key1')
+
+      @p.update('key1') do |v|
+        (v.to_i * 2).to_s
+      end
+      assert_equal '2', @p.get('key1')
+
+      @p.save # stores all data into file
+
+      assert File.exist?(storage_path)
+
+      @p.put('key2', 4)
+
+      @d.stop; @d.before_shutdown; @d.shutdown; @d.after_shutdown; @d.close; @d.terminate
+
+      assert_equal({'key1' => '2', 'key2' => 4}, File.open(storage_path){|f| JSON.parse(f.read) })
+
+      # re-create to reload storage contents
+      @d = MyInput.new
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_false @p.store.empty?
+
+      assert_equal '2', @p.get('key1')
+      assert_equal 4, @p.get('key2')
+    end
+  end
+
+  sub_test_case 'configured with root-dir and plugin id' do
+    test 'works as storage which stores data under root dir' do
+      root_dir = File.join(TMP_DIR, 'root')
+      expected_storage_path = File.join(root_dir, 'worker0', 'local_storage_test', 'storage.json')
+      conf = config_element('ROOT', '', {'@id' => 'local_storage_test'})
+      Fluent::SystemConfig.overwrite_system_config('root_dir' => root_dir) do
+        @d.configure(conf)
+      end
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal expected_storage_path, @p.path
+      assert @p.store.empty?
+
+      assert_nil @p.get('key1')
+      assert_equal 'EMPTY', @p.fetch('key1', 'EMPTY')
+
+      @p.put('key1', '1')
+      assert_equal '1', @p.get('key1')
+
+      @p.update('key1') do |v|
+        (v.to_i * 2).to_s
+      end
+      assert_equal '2', @p.get('key1')
+
+      @p.save # stores all data into file
+
+      assert File.exist?(expected_storage_path)
+
+      @p.put('key2', 4)
+
+      @d.stop; @d.before_shutdown; @d.shutdown; @d.after_shutdown; @d.close; @d.terminate
+
+      assert_equal({'key1' => '2', 'key2' => 4}, File.open(expected_storage_path){|f| JSON.parse(f.read) })
+
+      # re-create to reload storage contents
+      @d = MyInput.new
+      Fluent::SystemConfig.overwrite_system_config('root_dir' => root_dir) do
+        @d.configure(conf)
+      end
+      @d.start
+      @p = @d.storage_create()
+
+      assert_false @p.store.empty?
+
+      assert_equal '2', @p.get('key1')
+      assert_equal 4, @p.get('key2')
+    end
+  end
+
+  sub_test_case 'persistent specified' do
+    test 'works well with path' do
+      omit "It's hard to test on Windows" if Fluent.windows?
+
+      storage_path = File.join(TMP_DIR, 'my_store.json')
+      conf = config_element('ROOT', '', {}, [config_element('storage', '', {'path' => storage_path, 'persistent' => 'true'})])
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal storage_path, @p.path
+      assert @p.store.empty?
+
+      assert_nil @p.get('key1')
+      assert_equal 'EMPTY', @p.fetch('key1', 'EMPTY')
+
+      @p.put('key1', '1')
+      assert_equal({'key1' => '1'}, File.open(storage_path){|f| JSON.parse(f.read) })
+
+      @p.update('key1') do |v|
+        (v.to_i * 2).to_s
+      end
+      assert_equal({'key1' => '2'}, File.open(storage_path){|f| JSON.parse(f.read) })
+    end
+
+    test 'works well with root-dir and plugin id' do
+      omit "It's hard to test on Windows" if Fluent.windows?
+
+      root_dir = File.join(TMP_DIR, 'root')
+      expected_storage_path = File.join(root_dir, 'worker0', 'local_storage_test', 'storage.json')
+      conf = config_element('ROOT', '', {'@id' => 'local_storage_test'}, [config_element('storage', '', {'persistent' => 'true'})])
+      Fluent::SystemConfig.overwrite_system_config('root_dir' => root_dir) do
+        @d.configure(conf)
+      end
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal expected_storage_path, @p.path
+      assert @p.store.empty?
+
+      assert_nil @p.get('key1')
+      assert_equal 'EMPTY', @p.fetch('key1', 'EMPTY')
+
+      @p.put('key1', '1')
+      assert_equal({'key1' => '1'}, File.open(expected_storage_path){|f| JSON.parse(f.read) })
+
+      @p.update('key1') do |v|
+        (v.to_i * 2).to_s
+      end
+      assert_equal({'key1' => '2'}, File.open(expected_storage_path){|f| JSON.parse(f.read) })
+    end
+
+    test 'raises error if it is configured to use on-memory storage' do
+      assert_raise Fluent::ConfigError.new("Plugin @id or path for <storage> required when 'persistent' is true") do
+        @d.configure(config_element('ROOT', '', {}, [config_element('storage', '', {'persistent' => 'true'})]))
+      end
+    end
+  end
+
+  sub_test_case 'with various configurations' do
+    test 'mode and dir_mode controls permissions of stored data' do
+      storage_path = File.join(TMP_DIR, 'dir', 'my_store.json')
+      storage_conf = {
+        'path' => storage_path,
+        'mode' => '0600',
+        'dir_mode' => '0777',
+      }
+      conf = config_element('ROOT', '', {}, [config_element('storage', '', storage_conf)])
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal storage_path, @p.path
+      assert @p.store.empty?
+
+      @p.put('key1', '1')
+      assert_equal '1', @p.get('key1')
+
+      @p.save # stores all data into file
+
+      assert File.exist?(storage_path)
+      assert_equal 0600, (File.stat(storage_path).mode % 01000)
+      assert_equal 0777, (File.stat(File.dirname(storage_path)).mode % 01000)
+    end
+
+    test 'pretty_print controls to write data in files as human-easy-to-read' do
+      storage_path = File.join(TMP_DIR, 'dir', 'my_store.json')
+      storage_conf = {
+        'path' => storage_path,
+        'pretty_print' => 'true',
+      }
+      conf = config_element('ROOT', '', {}, [config_element('storage', '', storage_conf)])
+      @d.configure(conf)
+      @d.start
+      @p = @d.storage_create()
+
+      assert_equal storage_path, @p.path
+      assert @p.store.empty?
+
+      @p.put('key1', '1')
+      assert_equal '1', @p.get('key1')
+
+      @p.save # stores all data into file
+
+      expected_pp_json = <<JSON.chomp
+{
+  "key1": "1"
+}
+JSON
+      assert_equal expected_pp_json, File.read(storage_path)
+    end
   end
 end