diff --git a/app/logical/storage_manager.rb b/app/logical/storage_manager.rb
index 4970dec26..b12d1f674 100644
--- a/app/logical/storage_manager.rb
+++ b/app/logical/storage_manager.rb
@@ -17,9 +17,9 @@ class StorageManager
   # @param base_url [String] the base URL where images are stored (ex: "https://cdn.donmai.us/")
   # @param base_dir [String] the base directory where images are stored (ex: "/var/www/danbooru/public/images")
   # @param tagged_filenames [Boolean] whether image URLs can include tags
-  def initialize(base_url:, base_dir:, tagged_filenames: Danbooru.config.enable_seo_post_urls)
-    @base_url = base_url.chomp("/")
-    @base_dir = base_dir
+  def initialize(base_url: nil, base_dir: nil, tagged_filenames: Danbooru.config.enable_seo_post_urls)
+    @base_url = base_url.to_s.chomp("/")
+    @base_dir = base_dir.to_s
     @tagged_filenames = tagged_filenames
   end
 
diff --git a/app/logical/storage_manager/mirror.rb b/app/logical/storage_manager/mirror.rb
new file mode 100644
index 000000000..b7dbcc24c
--- /dev/null
+++ b/app/logical/storage_manager/mirror.rb
@@ -0,0 +1,29 @@
+# A StorageManager that mirrors files across multiple storage backends.
+class StorageManager::Mirror < StorageManager
+  attr_reader :services
+
+  def initialize(services, **options)
+    @services = services
+    super(**options)
+  end
+
+  def store(io, dest_path)
+    services.each do |service|
+      service.store(io, dest_path)
+    end
+  end
+
+  def delete(path)
+    services.each do |service|
+      service.delete(path)
+    end
+  end
+
+  def open(path)
+    services.first.open(path)
+  end
+
+  def file_url(path)
+    services.first.file_url(path)
+  end
+end
diff --git a/test/unit/storage_manager_test.rb b/test/unit/storage_manager_test.rb
index 1b8c6fd95..ad054563b 100644
--- a/test/unit/storage_manager_test.rb
+++ b/test/unit/storage_manager_test.rb
@@ -38,4 +38,48 @@ class StorageManagerTest < ActiveSupport::TestCase
       end
     end
   end
+
+  context "StorageManager::Mirror" do
+    setup do
+      @temp_dir1 = Dir.mktmpdir("danbooru-temp1-")
+      @temp_dir2 = Dir.mktmpdir("danbooru-temp2-")
+
+      @storage_manager = StorageManager::Mirror.new([
+        StorageManager::Local.new(base_dir: @temp_dir1, base_url: "/data"),
+        StorageManager::Local.new(base_dir: @temp_dir2, base_url: "/data")
+      ])
+    end
+
+    teardown do
+      FileUtils.rm_rf(@temp_dir1)
+      FileUtils.rm_rf(@temp_dir2)
+    end
+
+    context "#store method" do
+      should "store the file on both backends" do
+        @storage_manager.store(StringIO.new("data"), "test.txt")
+
+        assert("data", File.read("#{@temp_dir1}/test.txt"))
+        assert("data", File.read("#{@temp_dir2}/test.txt"))
+      end
+    end
+
+    context "#delete method" do
+      should "delete the file from both backends" do
+        @storage_manager.store(StringIO.new("data"), "test.txt")
+        @storage_manager.delete("test.txt")
+
+        assert_not(File.exist?("#{@temp_dir1}/test.txt"))
+        assert_not(File.exist?("#{@temp_dir2}/test.txt"))
+      end
+    end
+
+    context "#open method" do
+      should "open the file from the first backend" do
+        @storage_manager.store(StringIO.new("data"), "test.txt")
+
+        assert_equal("data", @storage_manager.open("test.txt").read)
+      end
+    end
+  end
 end