RBS (Remote BLOB Storage) is the “answer” to that problem, and it’s straightforward to configure it to support the out-of-box FILESTREAM provider of SQL 2008, so you can pretty easily get document libraries moved into a folder on the SQL server. The process is multi-step (well documented on TechNet) but straightforward. In the end you have a folder (must be LOCAL on the SQL server–no NAS with the OOB RBS), and BLOBS are stored in the folder.
You cannot (SHOULD not) access the content directly in the folder. You always access it through SharePoint. If you use SP backup, it will back up (and restore) correctly. If you do not use SP backup–for example, if you use only SQL backups–then you need to back up the database (first) then the BLOB store folder (second).
There are performance considerations for RBS (planning) but bottom line is that a lot of scenarios–particularly those in which a SP document library is “replacing” a traditional file share–that RBS will work well. TechNet has lots of info–be sure to look at both the technical implementation AND planning docs.
<i>This question was answered by Spencer Harbar, Enterprise Architect at Microsoft and Dan Holme, Consultant and Trainer, Intellium.</i>