RBS includes a FILESTREAM provider that lets you use RBS to store BLOBs on an instance of SQL Server. If you want use RBS to store BLOBs in a different storage solution, you have to use a third party RBS provider developed for that storage solution, or develop a custom RBS provider using the RBS API. A sample provider that stores BLOBs in the NTFS file system is available as a learning resource on Codeplex.