The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 1: Storing and Managing Unstructured DataEnter FILESTREAMBy now it should be very clear that storing LOB data in the database offers a number ofbenefits, but introduces performance challenges. Conversely, storing the LOB data in thefile system has overriding performance advantages, but fails to offer some of the basicdata integrity, security, and manageability features that are required for business data,and which SQL Server provides.Up to now, most people have adopted file system storage by necessity, and often struggledto overcome the associated shortcomings. This is exactly where the new FILESTREAMfeature fits in. FILESTREAM storage, introduced in SQL Server 2008, is implementedas an extension to the VARBINARY(MAX) data type. In other words, SQL Server implementsFILESTREAM storage through VARBINARY(MAX) columns with an additional flagindicating that the BLOB data should be stored in the FILESTREAM data container. Itallows BLOBs to be stored in a special folder on the NTFS file system, while bringing thatdata under the transactional control of SQL Server. When a VARBINARY(MAX) column ismarked as a FILESTREAM column, the 2 GB storage limit SQL Server puts on large-valuetypes is no longer applicable.This new FILESTREAM attribute is only available on the VARBINARY(MAX) data type.It cannot be applied to the VARCHAR(MAX) data type. If you have large plain text valuesto store, you can opt to store them in a VARBINARY(MAX) FILESTREAM column anduse the CAST( AS VARCHAR(MAX)) method, if you need access to the plaintext data in a query. When accessing a CLOB stored in a FILESTREAM column usingthe FILESTREAM APIs (SqlFileStream managed class or the Win32 function,OpenSqlFileStream), you can use functions available in your programming languageof choice to convert the byte stream to plain text. For this reason, from this point on, we'lluse the generic term "BLOB" to refer to all forms of LOB data.Note that, to access FILESTREAM data through the streaming API, you must connect toSQL Server using Integrated Security (Windows authentication). If you connect to SQL37