Introducing Remote BLOB Storage

Remote BLOB Storage (RBS) is a library API set designed to move storage of large binary data (BLOBs) from Microsoft SQL Server to external storage solutions. RBS is incorporated as an add-on feature pack for Microsoft SQL Server 2008 and Microsoft SQL Server 2008 Express, and later SQL Server 2008 R2 and SQL Server 2008 R2 Express.

Using RBS, applications can store large amounts of unstructured data (such as Office documents, PDF files, or videos) and enjoy both the relational capabilities of SQL Server and the scalability of a dedicated blob store. Best of all, developers do not have to write the code to handle the job of tying together the SQL metadata and the blob data. RBS handles the transactional consistency completely.

An application stores and accesses blob data by calling into the RBS client library. ISVs and storage solution vendors can create their own RBS Provider Library to enable the use of custom stores with applications written against the RBS API set. Microsoft has even created a provider named FILESTREAM RBS provider, which comes with RBS 2008 R2 and can be used for storing BLOBs on the underlying NTFS file system. The FILESTREAM RBS provider ties the RBS technology with the FILESTREAM feature introduced in SQL Server 2008.

SharePoint 2007 did not take advantage of the recent SQL Server features that Microsoft introduced for unstructured data in SQL Server 2008, such as the FILESTREAM attribute or RBS technology; instead, SharePoint 2007 provided its own options to enhance the storage efficiency and manageability of huge data though External BLOB Storage (EBS).

SharePoint 2010 supports RBS and can leverage the SQL Server FILESTREAM RBS provider, thus providing cheaper storage and much better performance. Figure 9.16 illustrates how RBS works with SharePoint 2010.

Figure 9.16. Externalizing BLOB storage using RBS.

In SharePoint 2010, the FILESTREAM RBS provider can also be used to work around the 4GB database limitation in SQL Server Express. Unlike Windows SharePoint Services 3.0, SharePoint Foundation 2010 does not use the Windows Internal Database, which had no database size limit. Therefore, when Windows SharePoint Services 3.0 users are trying to upgrade their farms, they might fall into a scenario where they have an internal database larger than 4GB, which would exceed the limitation of SQL Server Express. At this point, they will be prompted to download the FILESTREAM RBS provider to use the underlying file system to externalize their BLOBs.