The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 3: Accessing FILESTREAM Data from Client Applicationsclosed and transaction is committed. The old FILESTREAM data file will be removed byan asynchronous garbage collector thread.Note that any UPDATE triggers that exist on the target table will be fired when theFILESTREAM file handle is closed.Partial updates to FILESTREAM dataA partial update involves replacing a part of an existing FILESTREAM data file with newcontent, or appending to the end of an existing BLOB file. Unlike partial updates onVARBINARY(MAX) columns, attempting partial updates on FILESTREAM cells is a veryslow operation because a new disk file will be created with the new file content every timethe contents change. This adds a lot of additional I/O requirements. In effect, there isno such thing as a partial update to a FILESTREAM data file so, if your business or applicationrequires frequent small partial updates to the BLOB data, you might want to useVARBINARY(MAX) columns rather than FILESTREAM storage.If necessary to support a legacy application, partial updates can be simulated by openingthe FILESTREAM data file for read-write access and then moving the file pointer tothe appropriate position before writing the new data to the desired location, eitheroverwriting existing data, or appending the data to the end of the file.Any UPDATE triggers that exist on the target table will be fired when the FILESTREAMfile handle is closed.104