For all of you who want to do this. Here goes:
If you run this on your MySQL database prior to doing a backup then you will get the number of records backed up etc then you can see how quickly your system is growing.
select table_catalog, table schema, table_name, table_type, table_rows, update_time from information_schema.tables where table_schema='alfresco';
run this against your information_schema database and it will show you the information you require.