diff --git a/orchestra/contrib/databases/backends.py b/orchestra/contrib/databases/backends.py
index f845c838..29e764ba 100644
--- a/orchestra/contrib/databases/backends.py
+++ b/orchestra/contrib/databases/backends.py
@@ -121,6 +121,10 @@ class MysqlDisk(ServiceMonitor):
     model = 'databases.Database'
     verbose_name = _("MySQL disk")
     delete_old_equal_values = True
+    doc_settings = (settings,
+        ('DATABASES_MYSQL_DB_DIR',)
+    )
+    mysql_db_dir = settings.DATABASES_MYSQL_DB_DIR
     
     def exceeded(self, db):
         if db.type != db.MYSQL:
@@ -141,11 +145,14 @@ class MysqlDisk(ServiceMonitor):
         )
         
     def prepare(self):
-        super(MysqlDisk, self).prepare()
+        super().prepare()
+        context = {
+            'mysql_db_dir': self.mysql_db_dir,
+        }
         self.append(textwrap.dedent("""\
-            function monitor () {
-                { du -bs "/var/lib/mysql/$1" || echo 0; } | awk {'print $1'}
-            }"""))
+            function monitor_mysql () {
+                { SIZE=$(du -bs "%(mysql_db_dir)s/$1") && echo $SIZE || echo 0; } | awk {'print $1'}
+            }""") % context)
         # Slower way
         #self.append(textwrap.dedent("""\
         #    function monitor () {
@@ -160,12 +167,13 @@ class MysqlDisk(ServiceMonitor):
         if db.type != db.MYSQL:
             return
         context = self.get_context(db)
-        self.append('echo %(db_id)s $(monitor "%(db_dirname)s")' % context)
+        self.append('echo %(db_id)s $(monitor_%(db_type)s "%(db_dirname)s")' % context)
     
     def get_context(self, db):
         context = {
             'db_name': db.name,
             'db_dirname': db.name.replace('-', '@003f'),
             'db_id': db.pk,
+            'db_type': db.type,
         }
         return replace(replace(context, "'", '"'), ';', '')
diff --git a/orchestra/contrib/databases/settings.py b/orchestra/contrib/databases/settings.py
index fe69e8dc..24dcfa68 100644
--- a/orchestra/contrib/databases/settings.py
+++ b/orchestra/contrib/databases/settings.py
@@ -22,3 +22,8 @@ DATABASES_DEFAULT_HOST = Setting('DATABASES_DEFAULT_HOST',
     'localhost',
     validators=[validate_hostname],
 )
+
+
+DATABASES_MYSQL_DB_DIR = Setting('DATABASES_MYSQL_DB_DIR',
+    '/var/lib/mysql',
+)
diff --git a/orchestra/contrib/saas/README.md b/orchestra/contrib/saas/README.md
new file mode 100644
index 00000000..3aec7396
--- /dev/null
+++ b/orchestra/contrib/saas/README.md
@@ -0,0 +1,79 @@
+# SaaS - Software as a Service
+
+
+This app provides support for services that follow the SaaS model. Traditionaly known as multi-site or multi-tenant web applications where a single installation of a CMS provides accounts for multiple isolated tenants.
+
+
+## Service declaration
+
+Each service is defined by a `SoftwareService` subclass, you can find examples on the [`services` module](services).
+
+The minimal service declaration will be:
+
+```python
+class DrupalService(SoftwareService):
+    name = 'drupal'
+    verbose_name = "Drupal"
+    icon = 'orchestra/icons/apps/Drupal.png'
+    site_domain = settings.SAAS_MOODLE_DOMAIN
+```
+
+Additional attributes can be used to further customize the service class to your needs.
+
+### Custom forms
+If the service needs to keep track of additional information you should provide an extra form and serializer. For example, wordpress requires you to provide an email_address during account creation, and the assigned blog ID is required for effectively update account state or delete it. In this case we provide two forms:
+
+```python
+class WordPressForm(SaaSBaseForm):
+    email = forms.EmailField(label=_("Email"),
+        help_text=_("A new user will be created if the above email address is not in the database.<br>"
+                    "The username and password will be mailed to this email address."))
+
+class WordPressChangeForm(WordPressForm):
+    blog_id = forms.IntegerField(label=("Blog ID"), widget=widgets.SpanWidget, required=False,
+        help_text=_("ID of this blog used by WordPress, the only attribute that doesn't change."))
+```
+
+WordPressForm provides the email field, and WordPressChangeForm adds the `blog_id` on top of it. `blog_id` will be represented as a *readonly* field on the form, so no modification will be allowed.
+
+### Serializer for extra data
+
+Additionally, we should provide a serializer in order to save the form extra pices of information into the database (into field *data*).
+
+```python
+class WordPressDataSerializer(serializers.Serializer):
+    email = serializers.EmailField(label=_("Email"))
+    blog_id = serializers.IntegerField(label=_("Blog ID"), allow_null=True, required=False)
+```
+
+Now we have everything needed for declaring the WordPress service.
+
+```python
+class WordPressService(SoftwareService):
+    name = 'wordpress'
+    verbose_name = "WordPress"
+    form = WordPressForm
+    change_form = WordPressChangeForm
+    serializer = WordPressDataSerializer
+    icon = 'orchestra/icons/apps/WordPress.png'
+    change_readonly_fields = ('email', 'blog_id')
+    site_domain = settings.SAAS_WORDPRESS_DOMAIN
+    allow_custom_url = settings.SAAS_WORDPRESS_ALLOW_CUSTOM_URL
+```
+
+Notice that two optional forms can be provices `form` and `change_form`. When non of them is provided, SaaS will provide a default one for you. When only `form` is provided, it will be used for both, *add view* and *change view*. If both are provided, `form` will be used for the *add view* and `change_form` for the change view. This last option allows us to display the `blog_id` back to the user, only when we have it (after creation).
+
+`change_readonly_fields` is a tuple with the name of the fields that can not be edditied once the service has been created.
+
+
+## Backend
+
+
+A backend class is required to interface with the web application and perform `save()` and `delete()` operations on it. The more reliable way of interfacing with the application is by means of a CLI (e.g. [Moodle](backends/moodle.py), but not all CMS come with this tool. The second preferable way is using some sort of API, possibly HTTP-based (e.g. [gitLab](backends/gitlab.py). This is less realiable because additional moving parts are used underneeth the interface; a busy web server can timeout our requests. The least prefered way is interfacing with an HTTP-HTML interface designed for human consumption, really paintful to implement but sometimes is the only way (e.g. [WordPress](backends/wordpressmu.py)).
+
+Some applications do not support multi-tenancy by default, but we can hack the configuration file of such apps and generate *table prefix* or *database name* based on some property of the URL. Example of this services are [moodle](backends/moodle.py) and [phplist](backends/phplist.py) respectively.
+
+
+## Settings
+
+Enabled services should be added into the `SAAS_ENABLED_SERVICES` settings tuple, providing its full module path, e.g. `'orchestra.contrib.saas.services.moodle.MoodleService'`. Parameters that should allow easy configuration on each deployment should be defined as settings. e.g. `SAAS_WORDPRESS_DOMAIN`. Take a look at the [`settings` module](settings.py).