What is FILESTREAM?
FILESTREAM is a SQL Server 2008 feature to store BLOB content on to file system. From FILESTREAM Overview: FILESTREAM integrates the SQL Server Database Engine with an NTFS file system by storing varbinary(max) binary large object (BLOB) data as files on the file system. Transact-SQL statements can insert, update, query, search, and back up FILESTREAM data. Win32 file system interfaces provide streaming access to the data. FILESTREAM uses the NT system cache for caching file data. This helps reduce any effect that FILESTREAM data might have on Database Engine performance. The SQL Server buffer pool is not used; therefore, this memory is available for query processing. SQL FILESTREAM feature does not allow to store content on anything other than local storages.