You don't need to write your own provider if you're using SQL Server and you understand the way it uses the aspnet tables. Your task would be to ensure that you are backing up those tables and you need to consider those tables as being part of your essential database. Some people make the mistake of ignoring those aspnet tables and they put themselves at risk that way.

Every system developer needs to document the tables used by the system, along with a description. And the backup and recovery plan needs to include all those tables, which is mostly a concern if you don't perform backups by copying the entire DB verbatim. Lots of people perform delta backups of tables, especially for cases where the tables are huge and a full backup can't reasonably be done on a daily basis. But this is a big subject and I don't want to get into too deep in this forum.

There are many web pages that discuss writing your own providers if you're an advanced developer and you have a reason to do that. It's not easy and it's way to easy to do it wrong, so I don't suggest this for most people. If you get it wrong you are placing a lot of data in jeopardy.

Eric