Merge pull request platformsh#1385 from sdaugherty/patch-1

Document dedicated limitation regarding MyISAM tables

src/configuration/services/mysql.md

@@ -26,6 +26,8 @@ The service types `mariadb` and `mysql` both refer to MariaDB for compatibility
 > **note**
 >
 > Downgrades of MySQL or MariaDB are not supported. Both will update their own datafiles to a new version automatically but cannot downgrade them. If you want to experiment with a later version without committing to it use a non-master environment.
+>
+> Dedicated environments do not support any storage engine other than InnoDB. Tables created using the MyISAM storage engine on dedicated environments will not replicate between cluster nodes.
 
 ### Deprecated versions
 
@@ -199,6 +201,17 @@ ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_
 
 Consult the [MySQL documentation](https://dev.mysql.com/doc/refman/8.0/en/charset-mysql.html) for further details.
 
+## Storage Engine
+
+We recommend using the InnoDB storage engine wherever possible. MyISAM is only properly supported in Grid environments. In dedicated cluster environments there is no replication of MyISAM tables.
+
+If MyISAM tables are inadventently created or imported in a dedicated environment they can be converted to use the InnoDB storage engine using the following procedure:
+
+```sql
+RENAME TABLE <existing> <old>;
+INSERT INTO <existing> SELECT * from <old>;
+```
+
 ## Access your MariaDB service
 
 Assuming your MariaDB relationship is named `database`, the host name and port number obtained from `PLATFORM_RELATIONSHIPS` would be `database.internal` and `3306`. Open an [SSH session](/development/ssh.md) and run the MySQL command line client.