Regarding the Space Used tool wrongly reporting database being MySQL instead of MariaDB I think the root cause is the following code (direct link source on GitHub):
public static DatabaseProduct toProduct(String productNameOrJDBCScheme) { // ... else if (isMySQL(productNameOrJDBCScheme)) { product = MYSQL; } // ... } // ... private static boolean isMySQL(String productNameOrJDBCScheme) { return matches(productNameOrJDBCScheme, MYSQL) || matches(productNameOrJDBCScheme, MARIADB); }
The explanation of this behavior is explain in XWIKI-17912 description.
I drafted a pull request to try to fix that: https://github.com/xwiki/xwiki-platform/pull/3530